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Antarctic firn presents an exotic seismological environment in which the behaviors of propagating waves can be significantly at odds with those in other Earth media. We present a condensed view of the nascent field of ambient noise seismology in Antarctic firn-covered media, and highlight multiple unusual and information-rich observations framed through the lens of the firn's important role as a buffer for air temperature anomalies and a complex contributor to ice mass balance. We summarize key results from several recent papers depicting novel wind-excited firn resonances and point to the plethora of ways these observations could facilitate imaging and monitoring of glacial systems at single, isolated seismometers. Finally, we propose significant instrumental and computational objectives necessary to constrain resonance excitation mechanisms and broadly apply these observations as useful monitoring tools in Antarctica. [ABSTRACT FROM AUTHOR]

Antarctic firn presents an exotic seismological environment in which the behaviors of propagating waves can be significantly at odds with those in other Earth media. We present a condensed view of the nascent field of ambient noise seismology in Antarctic firn-covered media, and highlight multiple unusual and information-rich observations framed through the lens of the firn's important role as a buffer for air temperature anomalies and a complex contributor to ice mass balance. We summarize key results from several recent papers depicting novel wind-excited firn resonances and point to the plethora of ways these observations could facilitate imaging and monitoring of glacial systems at single, isolated seismometers. Finally, we propose significant instrumental and computational objectives necessary to constrain resonance excitation mechanisms and broadly apply these observations as useful monitoring tools in Antarctica. [ABSTRACT FROM AUTHOR]

The ice flow velocity is a basic feature of glaciers and ice sheets. Measuring ice flow velocities is very important for estimating the mass balance of ice sheets in the Arctic and Antarctic. Traditional methods for measuring ice flow velocity include the use of stakes, snow pits and on-site geodetic GPS and remote sensing measurement methods. Geodetic GPS measurements have high accuracy, but geodetic GPS monitoring points only sparsely cover the Antarctic ice sheets. Moreover, the resolution and accuracy of ice flow velocities based on remote sensing measurements are low. Although the accuracy of the location data recorded by the navigation-grade GPS receivers embedded in short-period seismographs is not as good as that of geodetic GPS, the ice flow velocity can be accurately measured by these navigation-grade GPS data collected over a sufficiently long period. In this paper, navigation-grade GPS location data obtained by passive seismic observations during the 36th Chinese National Antarctic Research Expedition were used to accurately track the movement characteristics of the ice sheet in the Larsemann Hills of East Antarctica and the Taishan Station area. The results showed that the ice sheet in the two study areas is basically moving northwestward with an average ice flow velocity of approximately 1 m mon−1. The results in the Taishan Station area are basically consistent with the geodetic GPS results, indicating that it is feasible to use the embedded GPS location data from short-period seismographs to track the movement characteristics of ice sheets. The ice flow characteristics in the Larsemann Hills are more complex. The measured ice flow velocities in the Larsemann Hills with a resolution of 200 m help to understand its characteristics. In summary, the ice flow velocities derived from GPS location data are of great significance for studying ice sheet dynamics and glacier mass balance and for evaluating the systematic errors caused by ice sheet movements in seismic imaging. [ABSTRACT FROM AUTHOR]

The ice cap covering Antarctica has long limited our understanding of the continental-scale crustal model due to its inaccessibility and the resulting logistical difficulties when executing geophysical field work, such as seismograph deployment. Resolving a high spatial resolution crustal model for Antarctica where seismographs are sparsely distributed stimulates scientific interest in this relatively less studied continent. In this study, we utilize satellite gravity observations from the global gravity model EIGEN-6C4 to create an alternative crustal thickness model of Antarctica. The gravity data were corrected for sediments, topography and ice cover. Furthermore, we considered the gravity effect due to vertical deformation of the lithosphere caused by ice load besides the earth's curvature in the modelling. We inverted the corrected gravity data using the regularized Bott's inversion method in spherical approximation and constrained the results by seismic observations. This crustal thickness model shows a thicker average crust in East Antarctica and a thinner one in West Antarctica. The thickest crust is in the Gamburtsev Subglacial Mountains with a Moho depth of over 40 km. The thicker crust is particularly evident along the Transantarctic Mountains and the Dronning Maud lands. Comparisons with existing models show a good correlation in gravity-constrained areas. Differences appear in the sedimentary basins and crust with thickness closer to seismic point observations. Overall, our crustal model is relatively improved than the existing gravity derived models. [ABSTRACT FROM AUTHOR]

Understanding deformation in ice shelves is necessary to evaluate the response of ice shelves to thinning. We study microseismicity associated with ice shelf deformation using nine broadband seismographs deployed near a rift on the Ross Ice Shelf. From December 2014 to November 2016, we detect 5,948 icequakes generated by rift deformation. Locations were determined for 2,515 events using a least squares grid‐search and double‐difference algorithms. Ocean swell, infragravity waves, and a significant tsunami arrival do not affect seismicity. Instead, seismicity correlates with tidal phase on diurnal time scales and inversely correlates with air temperature on multiday and seasonal time scales. Spatial variability in tidal elevation tilts the ice shelf, and seismicity is concentrated while the shelf slopes downward toward the ice front. During especially cold periods, thermal stress and embrittlement enhance fracture along the rift. We propose that thermal stress and tidally driven gravitational stress produce rift seismicity with peak activity in the winter. Plain Language Summary: In Antarctica, large bodies of floating ice called ice shelves help prevent ice on land from sliding into the ocean. To predict how Antarctica might respond to climate change, we need to understand how ice shelves interact with the environment, including the atmosphere and the ocean. The largest ice shelf, the Ross Ice Shelf, is over 500,000 km2 in area, making it the largest body of floating ice in the world. In this study, we deployed nine seismographs, the same instruments used to study earthquakes, to monitor vibrations and cracking within the Ross Ice Shelf over a 2‐year period. During that time, the instruments detected nearly 6,000 fracture events along a 120‐km‐long crack in the ice shelf. We compared the timing of the cracking to air temperature data, ocean wave activity, and tides to see whether these factors influenced the crack's behavior. We found that fracture occurs most frequently just after high tide during winter and when the air is very cold. We also found that fracture at the rift is not triggered by ocean waves. This work demonstrates that Antarctic ice shelves are very sensitive to the environment and highlights the need to continue studying them. Key Points: 2,515 icequakes associated with rift deformation on the Ross Ice Shelf are located using a double‐difference location algorithmIcequake timing correlates with tidal phase diurnally and inversely correlates with air temperature on multiday and seasonal time scalesOcean swell, infragravity waves, and a significant tsunami arrival are not correlated with increased rift activity [ABSTRACT FROM AUTHOR]

Abstract Erebus is an intraplate stratovolcano of phonolitic composition located at the southern end of Terror Rift within the West Antarctica Rift system. The volcanic edifice of Erebus exhibits a summit plateau that hosts the main crater and a smaller inner crater that contains a persistent lava lake. Volcano-seismic signals are recorded at Erebus by a permanent network of short-period and broadband seismometers installed around the volcano edifice. We investigate the duration-amplitude scaling of tremor recorded by the closest (~0.6–2 km) broadband stations to the inner crater during May 2002–April 2004 in order to elucidate the physical processes taking place at its source. After screening the data for signals related to non-volcanic sources such as iceberg calving, we obtained 72 tremor events. Spectral analysis reveals that these events were either harmonic exhibiting several overtones or broadband, but there were also mixed events that contained both of these two states. All tremor episodes considered in this study follow an exponential duration-amplitude distribution that implies a scale-bound source process. This precludes the possibility that any of these signals is related to iceberg calving near Ross island, or that rock fracturing processes play any role in tremor generation. The large viscosity of phonolitic magma (~105.3 Pa s) suggests that source mechanisms which require high flow speeds in order to excite tremor are unlikely to operate at Erebus. On the other hand, oscillations of CO 2 bubble clouds formed at localized asperities within the magma chamber represent a scale-bound source that is also consistent with the observed oxidation state of ascending gas and with the deep (~5–7 km) location of the tremor source. These results are important for understanding tremor processes at volcanoes which, similar to Erebus, exhibit vigorous convection in their shallow plumbing system. Highlights • Tremor events at Erebus exhibit an exponential scaling of duration-amplitude distribution. • The source of tremor at Erebus is scale-bound with characteristic scale length. • Resonance of bubble clouds within the plumbing system is a plausible tremor source. [ABSTRACT FROM AUTHOR]

SUMMARY Upper-mantle structure between 100 and 300 km depth below the northern Antarctic Peninsula is imaged by modelling P-wave traveltime residuals from teleseismic events recorded on the King Sejong Station (KSJ), the Argentinean/Italian stations (JUBA and ESPZ), an IRIS/GSN Station (PMSA) and the Seismic Experiment in Patagonia and Antarctica (SEPA) broad-band stations. For measuring traveltime residuals, we applied a multichannel cross-correlation method and inverted for upper-mantle structure using VanDecar's method. The new 3-D velocity model reveals a subducted slab with a ∼70° dip angle at 100-300 km depth and a strong low-velocity anomaly confined below the SE flank of the central Bransfield Basin. The low velocity is attributed to a thermal anomaly in the mantle that could be as large as 350-560 K and which is associated with high heat flow and volcanism in the central Bransfield Basin. The low-velocity zone imaged below the SE flank of the central Bransfield Basin does not extend under the northern Bransfield Basin, suggesting that the rifting process in that area likely involves different geodynamic processes. [ABSTRACT FROM AUTHOR]

The article focuses on the seismic observations of glaciogenic ocean waves on icebergs and ice shelves in the Ross Sea and on the Ross Ice Shelf in Antarctica. Investigation shows that the impulsive sources of ocean surface waves are frequent in the ice-shelf and iceberg-covered environment of coastal Antarctica. Field deployment of seismometers suggests that these impulsive events are generated through glaciological mechanisms. These mechanisms include small-scale calving and edge wasting of icebergs and ice-shelf fronts, edge-on-edge closing and opening associated with iceberg collisions and the impulsive opening of void space related to ice-shelf rifting. Observations offer a background of glaciogenic ocean-wave phenomena significant to the Ross Sea.

Focuses on the developments in digital stations of the Global Seismograph Network located in Antarctica, as of December 1995. Efforts of the stations in recording seismic data for over 30 years; Information on a training undergone by technicians in system maintenance and seismogram interpretation; Plan for the relocation of the South Pole seismic station several kilometers from the present habitation.