Larsen C Ice Shelf Research Articles

Holocene glacial activity in Barilari Bay, west Antarctic Peninsula, tracked by magnetic mineral assemblages: Linking ice, ocean, and atmosphere

AbstractWe investigate the origin and fate of lithogenic sediments using magnetic mineral assemblages in Barilari Bay, west Antarctic Peninsula (AP) from sediment cores recovered during the Larsen Ice Shelf System, Antarctica (LARISSA) NBP10‐01 cruise. To quantify and reconstruct Holocene changes in covarying magnetic mineral assemblages, we adopt an unsupervised mathematical unmixing strategy and apply it to measurements of magnetic susceptibility as a function of increasing temperature. Comparisons of the unmixed end‐members with magnetic observations of northwestern AP bedrock and the spatial distribution of magnetic mineral assemblages within the fjord, allow us to identify source regions, including signatures for “inner bay,” “outer bay,” and “northwestern AP” sources. We find strong evidence that supports the establishment of a late Holocene ice shelf in the fjord coeval with the Little Ice Age. Additionally, we present new evidence for late Holocene sensitivity to conditions akin to positive mean Southern Annual Mode states for western AP glaciers at their advanced Neoglacial positions.

Revealing the early ice flow patterns with historical Declassified Intelligence Satellite Photographs back to 1960s

AbstractThe reconnaissance ARGON satellites collected the earliest images of Antarctica from space dating back to the 1960s, providing valuable historical baseline information for studying polar ice sheets. Those photographs are underutilized for ice motion mapping, due to lack of sufficient ground controls for image orthorectification. In this study, we orthorectified the ARGON photographs by fully exploiting the metric qualities of WorldView satellite images: very high spatial resolution and precise geolocation. Through a case study over Larsen Ice Shelf, we demonstrated that the camera model with bundle block adjustment can achieve geolocation accuracy of better than the nominal resolution (140 m) for orthorectifying ARGON images, with WorldView imagery as ground control source. This allowed us to extend the ice velocity records of Larsen Ice Shelf back into 1960s~1970s for the first time. The retrospective analysis revealed that acceleration of the collapsed Larsen B occurred much earlier than previously thought.

Technologies for retrieving sediment cores in Antarctic subglacial settings.

Accumulations of sediment beneath the Antarctic Ice Sheet contain a range of physical and chemical proxies with the potential to document changes in ice sheet history and to identify and characterize life in subglacial settings. Retrieving subglacial sediments and sediment cores presents several unique challenges to existing technologies. This paper briefly reviews the history of sediment sampling in subglacial environments. It then outlines some of the technological challenges and constraints in developing the corers being used in sub-ice shelf settings (e.g. George VI Ice Shelf and Larsen Ice Shelf), under ice streams (e.g. Rutford Ice Stream), at or close to the grounding line (e.g. Whillans Ice Stream) and in subglacial lakes deep under the ice sheet (e.g. Lake Ellsworth). The key features of the corers designed to operate in each of these subglacial settings are described and illustrated together with comments on their deployment procedures.

Foehn winds link climate‐driven warming to ice shelf evolution in Antarctica

AbstractRapid warming of the Antarctic Peninsula over the past several decades has led to extensive surface melting on its eastern side, and the disintegration of the Prince Gustav, Larsen A, and Larsen B ice shelves. The warming trend has been attributed to strengthening of circumpolar westerlies resulting from a positive trend in the Southern Annular Mode (SAM), which is thought to promote more frequent warm, dry, downsloping foehn winds along the lee, or eastern side, of the peninsula. We examined variability in foehn frequency and its relationship to temperature and patterns of synoptic‐scale circulation using a multidecadal meteorological record from the Argentine station Matienzo, located between the Larsen A and B embayments. This record was further augmented with a network of six weather stations installed under the U.S. NSF LARsen Ice Shelf System, Antarctica, project. Significant warming was observed in all seasons at Matienzo, with the largest seasonal increase occurring in austral winter (+3.71°C between 1962–1972 and 1999–2010). Frequency and duration of foehn events were found to strongly influence regional temperature variability over hourly to seasonal time scales. Surface temperature and foehn winds were also sensitive to climate variability, with both variables exhibiting strong, positive correlations with the SAM index. Concomitant positive trends in foehn frequency, temperature, and SAM are present during austral summer, with sustained foehn events consistently associated with surface melting across the ice sheet and ice shelves. These observations support the notion that increased foehn frequency played a critical role in precipitating the collapse of the Larsen B ice shelf.

Oceanic and atmospheric forcing of Larsen C Ice-Shelf thinning

Abstract. The catastrophic collapses of Larsen A and B ice shelves on the eastern Antarctic Peninsula have caused their tributary glaciers to accelerate, contributing to sea-level rise and freshening the Antarctic Bottom Water formed nearby. The surface of Larsen C Ice Shelf (LCIS), the largest ice shelf on the peninsula, is lowering. This could be caused by unbalanced ocean melting (ice loss) or enhanced firn melting and compaction (englacial air loss). Using a novel method to analyse eight radar surveys, this study derives separate estimates of ice and air thickness changes during a 15-year period. The uncertainties are considerable, but the primary estimate is that the surveyed lowering (0.066 ± 0.017 m yr−1) is caused by both ice loss (0.28 ± 0.18 m yr−1) and firn-air loss (0.037 ± 0.026 m yr−1). The ice loss is much larger than the air loss, but both contribute approximately equally to the lowering because the ice is floating. The ice loss could be explained by high basal melting and/or ice divergence, and the air loss by low surface accumulation or high surface melting and/or compaction. The primary estimate therefore requires that at least two forcings caused the surveyed lowering. Mechanisms are discussed by which LCIS stability could be compromised in the future. The most rapid pathways to collapse are offered by the ungrounding of LCIS from Bawden Ice Rise or ice-front retreat past a "compressive arch" in strain rates. Recent evidence suggests that either mechanism could pose an imminent risk.

Predicting early life connectivity of Antarctic silverfish, an important forage species along the Antarctic Peninsula

The early life stages of the Antarctic silverfish (Pleuragramma antarctica), an important prey species for higher predators in the Southern Ocean ecosystem, dominate the larval fish assemblages of the Bransfield Strait, one of the most important areas for larval retention off the Antarctic Peninsula. Nevertheless, the spatial location of areas where they were spawned and the timing of larval hatching remain unknown. By linking Lagrangian particle tracking simulations with age data obtained using otolith microincrements from fish caught north of Joinville Island in a pelagic survey, we estimated the distribution of hatch dates and subsequent growth rates of silverfish reaching the Bransfield Strait, and predicted the areas where they were spawned. Larval hatching peaked during the last week of December, and the inner shelf and shelf break, east of the Larsen Ice shelf, were the dominant areas predicted to contribute to larval assemblages in the Bransfield Strait. Over simulated periods of 600–630 days, 35–40% of particles remained within the Bransfield Strait, suggesting an important source of supply to higher predators feeding off the northern Antarctic Peninsula. The daily growth rate at the mean size of 22.3 mm was 0.18 mm, corresponding to a daily change in size of approximately 0.82% standard length (SL), and large variability in growth rate suggested a wide range of environmental conditions experienced during the period of advection from the spawning areas. These results provide spatial predictions that can be tested empirically in future studies, using the simulated trajectories to inform sampling design and spatial coverage.

Spatial–temporal patterns of surface melting observed over Antarctic ice shelves using scatterometer data

AbstractIce shelves fringing Antarctica are sensitive indicators of climate change due to the direct interface with the atmosphere and ocean. Meltwater induced by atmospheric warming percolates from the surface into hydrofractures and affects shelf stability. Surface melting reduces the microwave backscattering; thus backscatter data is useful in melt monitoring. The Ku-band scatterometer derived melting index (MI) was utilized to assess the decadal (2000–10) variability observed over Antarctic ice shelves. The low intensity melting observed over large ice shelves and high intensity melting observed over the Larsen, Amery, West and Shackleton ice shelves are discussed. A correlation of around 93% was observed between MI variation and rift propagation over Amery Ice Shelf. The El Niño and the Southern Oscillation (ENSO) correlation with MI was also investigated. The paper highlights that scatterometer derived information has the potential to assess meltwater production and rift propagation.

Precursors of Antarctic Bottom Water formed on the continental shelf off Larsen Ice Shelf

The dense water flowing out from the Weddell Sea significantly contributes to Antarctic Bottom Water (AABW) and plays an important role in the Meridional Overturning Circulation. The relative importance of the two major source regions, the continental shelves in front of Filchner-Ronne Ice Shelf and Larsen Ice Shelf, however, remains unclear. Several studies focused on the contribution of the Filchner-Ronne Ice Shelf region for the deep and bottom water production within the Weddell Gyre, but the role of the Larsen Ice Shelf region for this process, especially the formation of deep water, remains speculative. Measurements made during the Polarstern cruise ANT XXIX-3 (2013) add evidence to the importance of the source in the western Weddell Sea. Using Optimum Multiparameter analysis we show that the dense water found on the continental shelf in front of the former Larsen A and B together with a very dense water originating from Larsen C increases the thickness and changes the θ/S characteristics of the layer that leaves the Weddell Sea to contribute to AABW.

Foehn warming distributions in nonlinear and linear flow regimes: a focus on the Antarctic Peninsula

The structure of lee‐side warming during foehn events is investigated as a function of cross‐barrier flow regime linearity. Two contrasting cases of westerly flow over the Antarctic Peninsula (AP) are considered – one highly nonlinear, the other relatively linear. Westerly flow impinging on the AP provides one of the best natural laboratories in the world for the study of foehn, owing to its maritime setting and the Larsen C Ice Shelf (LCIS) providing an expansive, homogeneous and smooth surface on its east side. Numerical simulations with the Met Office Unified Model (at 1.5 km grid size) and aircraft observations are utilized. In case A, relatively weak southwesterly cross‐Peninsula flow and an elevated upwind inversion dictate a highly nonlinear foehn event, with mountain wave breaking observed. The consequent strongly accelerated downslope flow leads to high‐amplitude warming and ice‐shelf melt in the immediate lee of the AP. However this foehn warming diminishes rapidly downwind due to upward ascent of the foehn flow via a hydraulic jump. In case C, strong northwesterly winds dictate a relatively linear flow regime. There is no hydraulic jump and strong foehn winds are able to flow at low levels across the entire ice shelf, mechanically mixing the near‐surface flow, preventing the development of a strong surface inversion and delivering large fluxes of sensible heat to the ice shelf. Consequently, in case C ice‐melt rates are considerably greater over the LCIS as a whole than in case A. Our results imply that although nonlinear foehn events cause intense warming in the immediate lee of mountains, linear foehn events will commonly cause more extensive lee‐side warming and, over an ice surface, higher melt rates. This has major implications for the AP, where recent east‐coast warming has led to the collapse of two ice shelves immediately north of the LCIS.

Downslope föhn winds over the Antarctic Peninsula and their effect on the Larsen ice shelves

Abstract. Mesoscale model simulations are presented of a westerly föhn event over the Antarctic Peninsula mountain ridge and onto the Larsen C ice shelf, just south of the recently collapsed Larsen B ice shelf. Aircraft observations showed the presence of föhn jets descending near the ice shelf surface with maximum wind speeds at 250–350 m in height. Surface flux measurements suggested that melting was occurring. Simulated profiles of wind speed, temperature and wind direction were very similar to the observations. However, the good match only occurred at a model time corresponding to ~9 h before the aircraft observations were made since the model föhn jets died down after this. This was despite the fact that the model was nudged towards analysis for heights greater than ~1.15 km above the surface. Timing issues aside, the otherwise good comparison between the model and observations gave confidence that the model flow structure was similar to that in reality. Details of the model jet structure are explored and discussed and are found to have ramifications for the placement of automatic weather station (AWS) stations on the ice shelf in order to detect föhn flow. Cross sections of the flow are also examined and were found to compare well to the aircraft measurements. Gravity wave breaking above the mountain crest likely created a~situation similar to hydraulic flow and allowed föhn flow and ice shelf surface warming to occur despite strong upwind blocking, which in previous studies of this region has generally not been considered. Our results therefore suggest that reduced upwind blocking, due to wind speed increases or stability decreases, might not result in an increased likelihood of föhn events over the Antarctic Peninsula, as previously suggested. The surface energy budget of the model during the melting periods showed that the net downwelling short-wave surface flux was the largest contributor to the melting energy, indicating that the cloud clearing effect of föhn events is likely to be the most important factor for increased melting relative to non-föhn days. The results also indicate that the warmth of the föhn jets through sensible heat flux ("SH") may not be critical in causing melting beyond boundary layer stabilisation effects (which may help to prevent cloud cover and suppress loss of heat by convection) and are actually cancelled by latent heat flux ("LH") effects (snow ablation). It was found that ground heat flux ("GRD") was likely to be an important factor when considering the changing surface energy budget for the southern regions of the ice shelf as the climate warms.

Boundary condition of grounding lines prior to collapse, Larsen-B Ice Shelf, Antarctica.

Grounding zones, where ice sheets transition between resting on bedrock to full floatation, help regulate ice flow. Exposure of the sea floor by the 2002 Larsen-B Ice Shelf collapse allowed detailed morphologic mapping and sampling of the embayment sea floor. Marine geophysical data collected in 2006 reveal a large, arcuate, complex grounding zone sediment system at the front of Crane Fjord. Radiocarbon-constrained chronologies from marine sediment cores indicate loss of ice contact with the bed at this site about 12,000 years ago. Previous studies and morphologic mapping of the fjord suggest that the Crane Glacier grounding zone was well within the fjord before 2002 and did not retreat further until after the ice shelf collapse. This implies that the 2002 Larsen-B Ice Shelf collapse likely was a response to surface warming rather than to grounding zone instability, strengthening the idea that surface processes controlled the disintegration of the Larsen Ice Shelf.

Top-down rather than bottom-up change

Ice Sheets The Larsen-B Ice Shelf in Antarctica collapsed in 2002 because of a regional increase in surface temperature. This finding, reported by Rebesco et al. , will surprise many who supposed that the shelf's disintegration probably occurred because of thinning of the ice shelf and the resulting loss of support by the sea floor beneath it. The authors mapped the sea floor beneath the ice shelf before it fell apart, which revealed that the modern ice sheet grounding line was established around 12,000 years ago and has since remained unchanged. If the ice shelf did not collapse because of thinning from below, then it must have been caused by warming from above. Science , this issue p. [1354][1] [1]: /lookup/doi/10.1126/science.1256697

Surface energy budget on Larsen and Wilkins ice shelves in the Antarctic Peninsula: results based on reanalyses in 1989–2010

Abstract. Ice shelves in the Antarctic Peninsula have significantly disintegrated during recent decades. To better understand the atmospheric contribution in the process, we have analysed the inter-annual variations in radiative and turbulent surface fluxes and weather conditions over Larsen C Ice Shelf (LCIS) and Wilkins Ice Shelf (WIS) in the Antarctic Peninsula in 1989–2010. Three atmospheric reanalyses were applied: ERA-Interim by ECMWF, Climate Forecast System Reanalysis (CFSR) by NCEP, and JRA-25/JCDAS by the Japan Meteorological Agency. In addition, in situ observations from an automatic weather station (AWS) on LCIS were applied, mainly for validation of the reanalyses. The AWS observations on LCIS did not show any significant temperature trend, and the reanalyses showed warming trends only over WIS: ERA-Interim in winter (0.23 °C yr−1) and JRA-25/JCDAS in autumn (0.13 °C yr−1). In LCIS from December through August and in WIS from March through August, the variations of surface net flux were partly explained by the combined effects of atmospheric pressure, wind and cloud fraction. The explained variance was much higher in LCIS (up to 80%) than in WIS (26–27%). Summer melting on LCIS varied between 11 and 58 cm water equivalent (w.e.), which is comparable to previous results. The mean amount of melt days per summer on LCIS was 69. The high values of melting in summer 2001–2002 presented in previous studies on the basis of simple calculations were not supported by our study. Instead, our calculations based on ERA-Interim yielded strongest melting in summer 1992–1993 on both ice shelves. On WIS the summer melting ranged between 10 and 23 cm w.e., and the peak values coincided with the largest disintegrations of the ice shelf. The amount of melt on WIS may, however, be underestimated by ERA-Interim, as previously published satellite observations suggest that it suffers from a significant bias over WIS.

Phase‐sensitive FMCW radar system for high‐precision Antarctic ice shelf profile monitoring

Ice shelves fringe much of the Antarctic continent, and, despite being up to 2 km thick, are vulnerable to climate change. Owing to their role in helping to control the ice sheet contribution to sea level change there is great interest in measuring the rate at which they are melting into the ocean. This study describes the development and deployment of an ice-penetrating phase-sensitive FMCW radar, sufficiently robust and with sufficiently low-power consumption to be run through the Antarctic winter as a standalone instrument, yet with the stability and mm-precision needed to detect the very slow changes in ice shelf thickness in this exceptionally demanding environment. A number of elegant processing techniques are described to achieve reliable, high-precision performance and results presented on field data obtained from the Larsen-C ice shelf, Antarctica.

Utility of amino acids as biomarkers in polar marine sediments: a study on the continental shelf of Larsen region, Eastern Antarctic Peninsula

Ongoing global warming is affecting the polar regions at a faster pace than in many other lower latitude environments. Based on the idea that the changes at the sea surface leave a signal in the sedimentary record, we analysed the total hydrolysable amino acid (THAA) and enzymatically hydrolysable amino acid (EHAA) contents in sediments off the coast of the eastern Antarctic Peninsula during the decade following the collapse of sections A and B of the Larsen ice shelf to check their utility as biomarkers of this event. Two organic matter lability indexes (the EHAA-to-THAA ratio and the Dauwe degradation index) were also calculated to assess the quality of the organic matter in the sediment column. The THAA and EHAA concentrations in the upper 5 mm varied between ~1 and ~10 nmol mg−1 DW−1, corresponding to an oligotrophic environment, whereas the quality of the organic matter as indicated by the lability indexes was relatively high in the upper sediment column (<2 cm deep). The amino acid profiles and indexes in the sediment column were compared to the pigment profiles and indexes published in previous studies for the same stations. The results suggest that in the sediment column, pigments track more accurately than amino acids the pelagic organic matter supply to the seabed after the collapse of the Larsen ice shelf.

A Shift in the Biogenic Silica of Sediment in the Larsen B Continental Shelf, Off the Eastern Antarctic Peninsula, Resulting from Climate Change

In 2002, section B of the Larsen ice shelf, off of the Eastern Antarctic Peninsula, collapsed and created the opportunity to study whether the changes at the sea surface left evidence in the sedimentary record. Biogenic silica is major constituent of Antarctic marine sediment, and its presence in the sediment column is associated with diatom production in the euphotic zone. The abundance of diatom valves and the number of sponge spicules in the biogenic silica was analyzed to determine how the origin of the biogenic silica in the upper layers of the sediment column responded to recent environmental changes. Diatom valves were present only in the upper 2 cm of sediment, which roughly corresponds to the period after the collapse of the ice shelf. In contrast, sponge spicules, a more robust form of biogenic silica, were also found below the upper 2 cm layer of the sediment column. Our results indicate that in this region most of the biogenic silica in the sedimentary record originated from sponge spicules rather than diatoms during the time when the sea surface was covered by the Larsen ice shelf. Since the collapse of the ice shelf, the development of phytoplankton blooms and the consequent influx of diatom debris to the seabed have shifted the biogenic silica record to one dominated by diatom debris, as occurs in most of the Antarctic marine sediment. This shift provides further evidence of the anthropogenic changes to the benthic habitats of the Antarctic and will improve the interpretation of the sedimentary record in Polar Regions where these events occur.

In-situ aircraft observations of ice concentrations within clouds over the Antarctic Peninsula and Larsen Ice Shelf

Abstract. In-situ aircraft observations of ice crystal concentrations in Antarctic clouds are presented for the first time. Orographic, layer and wave clouds around the Antarctic Peninsula and Larsen Ice shelf regions were penetrated by the British Antarctic Survey's Twin Otter aircraft, which was equipped with modern cloud physics probes. The clouds studied were mostly in the free troposphere and hence ice crystals blown from the surface are unlikely to have been a major source for the ice phase. The temperature range covered by the experiments was 0 to −21 °C. The clouds were found to contain supercooled liquid water in most regions and at heterogeneous ice formation temperatures ice crystal concentrations (60 s averages) were often less than 0.07 l−1, although values up to 0.22 l−1 were observed. Estimates of observed aerosol concentrations were used as input into the DeMott et al. (2010) ice nuclei (IN) parameterisation. The observed ice crystal number concentrations were generally in broad agreement with the IN predictions, although on the whole the predicted values were higher. Possible reasons for this are discussed and include the lack of IN observations in this region with which to characterise the parameterisation, and/or problems in relating ice concentration measurements to IN concentrations. Other IN parameterisations significantly overestimated the number of ice particles. Generally ice particle concentrations were much lower than found in clouds in middle latitudes for a given temperature. Higher ice crystal concentrations were sometimes observed at temperatures warmer than −9 °C, with values of several per litre reached. These were attributable to secondary ice particle production by the Hallett Mossop process. Even in this temperature range it was observed that there were regions with little or no ice that were dominated by supercooled liquid water. It is likely that in some cases this was due to a lack of seeding ice crystals to act as rimers to initiate secondary ice particle production. This highlights the chaotic and spatially inhomogeneous nature of this process and indicates that the accurate representation of it in global models is likely to represent a challenge. However, the contrast between Hallett Mossop zone ice concentrations and the fairly low concentrations of heterogeneously nucleated ice suggests that the Hallet Mossop process has the potential to be very important in remote, pristine regions such as around the Antarctic coast.

Crustal structure of the Antarctic Peninsula sector of the Gondwana margin around Anvers Island from geophysical data

We investigated the crustal structure of the northern Antarctic Peninsula (AP) — a composite magmatic arc terrane at the Pacific margin of Gondwana. It was formed in Mesozoic–Cenozoic by collision/accretion of allochthonous terranes to the Gondwana margin during subduction and progressive ridge collision of former Phoenix Plate under the AP. The AP is distinguished by belts of high-amplitude, gravity and magnetic anomalies, inferred to indicate the presence of plutons of mafic composition comprising the huge AP batholith. For a better understanding of the lithosphere structure and tectonic processes of the AP continental margin we performed 2D gravity and magnetic modeling along line III-III, which crosses the margin south of Anvers Island. Our model incorporates data on seismic refraction (DSS-13) and reflection (line 8545-03) profiles and physical property data.Our modeling shows that the crust of the AP margin near Anvers Island is of continental type and comprises two crustal domains, which were welded together during mid-Cretaceous collision. On the east there is a thick (~40km), high-velocity/density continental crust of the Gondwana margin, which occupies the AP inner shelf and mainland, and Larsen Ice Shelf. The space between the Gondwanian block and oceanic crust of the Bellingshausen Sea is occupied by thinner (~26km) crust of lower densities of supposed accreted terrane, characterized by gravity anomalies caused probably by accretional tectonics as a result of Cretaceous subduction. Two belts of magnetic anomalies forming the PMA (Pacific Margin Anomaly) probably belong to different crustal domains: the western belt of the PMA relates to accretional block, while the eastern belt of the PMA corresponds to the Gondwana margin block. This may represent an evidence that the PMA relates to a tectono-magmatic event occurred after collision of Gondwana margin and accreted terrane (in mid-Cretaceous) and had been imprinted on already formed continental margin.

남극 지진 및 빙권 신호 관측을 위한 초광대역 지진계 설치

극지연구소는 2010 ~ 2011년 제 24차 남극하계탐사기간 동안 남극 킹조지섬에 3성분 초광대역 지진계를 성공적으로 설치하였다. 미국 IRIS PASSCAL에서 개발한 지진관측시스템을 활용하였으며, 이는 POLENET 지진관측시스템과 완벽히 호환된다. 지진계설치 및 운용의 목적은 크게 두가지로 나누어 지는데, 첫번째로 킹조지섬 주변의 지진 및 빙권관련 신호를 관측하는데 있으며, 두번째로는 극한환경에서의 지진관측장비 성능검사이다. 관측이 성공적으로 수행된다면, 다음 목표로 관측시스템의 추가확보를 통하여 남극반도 라르센 빙붕시스템과 같은 빙붕 주변으로 관측장소를 이동하여 지권과 빙권간 상호작용을 이해하고, 빙권의 움직임등 동역학적인 해석을 위한 연구를 수행하고자 한다. 이 보고서에서 우리는 지진파 배경잡음분석을 통하여 지진관측시스템 성능 및 특성 파악에 관한 내용과 관측시스템 운용관련 정보를 제공하고자 한다. Korea Polar Research Institute (KOPRI) has successfully installed two autonomous very broadband three-component seismic stations at the King George Island (KGI), Antarctica, during the 24th KOPRI Antarctic Summer Expedition (2010 ~ 2011). The seismic observation system is originally designed by the Incorporated Research Institutions for Seismology Program for Array Seismic Studies of the Continental Lithosphere Instrument Center, which is fully compatible with the Polar Earth Observing Network seismic system. The installation is to achieve the following major goals: 1. Monitoring local earthquakes and icequakes in and around the KGI, 2. Validating the robustness of seismic system operation under harsh environment. For further intensive studies, we plan to move and install them adding a couple more stations at ice shelf system, e.g., Larsen Ice Shelf System, Antarctica, in 2013 to figure out ice dynamics and physical interaction between lithosphere and cryosphere. In this article, we evaluate seismic station performance and characteristics by examining ambient noise, and provide operational system information such as frequency response and State-Of-Health information.

Brief communication &amp;quot;Can recent ice discharges following the Larsen-B ice-shelf collapse be used to infer the driving mechanisms of millennial-scale variations of the Laurentide ice sheet?&amp;quot;

Abstract. The effects of an ice-shelf collapse on inland glacier dynamics have recently been widely studied, especially since the breakup of the Antarctic Peninsula's Larsen-B ice shelf in 2002. Several studies have documented acceleration of the ice streams that were flowing into the former ice shelf. The mechanism responsible for such a speed-up lies with the removal of the ice-shelf backforce. Independently, it is also well documented that during the last glacial period, the Northern Hemisphere ice sheets experienced large discharges into the ocean, likely reflecting ice flow acceleration episodes on the millennial time scale. The classic interpretation of the latter is based on the existence of an internal thermo-mechanical feedback with the potential to generate oscillatory behavior in the ice sheets. Here we would like to widen the debate by considering that Larsen-B-like glacial analog episodes could have contributed significantly to the registered millennial-scale variablity.