199 results found
Siegert MJ, 2016, Vulnerable Antarctic ice shelves, Nature Climate Change, Vol: 7, Pages: 11-12, ISSN: 1758-6798
Standfirst: The decay of floating ice shelves around Antarctica speeds up ice flow from the continent and enhances sea-level rise. Now meltwater attributed to warm winds has been discovered on an East Antarctic ice shelf, suggesting greater vulnerability than previously thought.
Maritati A, Aitken ARA, Young DA, et al., 2016, The tectonic development and rrosion of the knox subglacial sedimentary basin, East Antarctica, Geophysical Research Letters, Vol: 43, Pages: 10728-10737, ISSN: 1944-8007
Sedimentary basins beneath the East Antarctic Ice Sheet (EAIS) have immense potential to inform models of the tectonic evolution of East Antarctica and its ice-sheet. However, even basic characteristics such as thickness and extent are often unknown. Using airborne geophysical data, we resolve the tectonic architecture of the Knox Subglacial Sedimentary Basin in western Wilkes Land. In addition, we apply an erosion restoration model to reconstruct the original basin geometry for which we resolve geometry typical of a transtensional pull-apart basin. The tectonic architecture strongly indicates formation as a consequence of the rifting of India from East Gondwana from ca. 160-130 Ma, and we suggest a spatial link with the western Mentelle Basin offshore Western Australia. The erosion restoration model shows that erosion is confined within the rift margins, suggesting that rift structure has strongly influenced the evolution of the Denman and Scott ice streams.
Kennicutt MC, Kim YD, Rogan-Finnemore M, et al., 2016, Delivering 21st century Antarctic and Southern Ocean science, Antarctic Science, Vol: 28, Pages: 407-423, ISSN: 1365-2079
The Antarctic Roadmap Challenges (ARC) project identified critical requirements to deliver high priority Antarctic research in the 21st century. The ARC project addressed the challenges of enabling technologies, facilitating access, providing logistics and infrastructure, and capitalizing on international co-operation. Technological requirements include: i) innovative automated in situ observing systems, sensors and interoperable platforms (including power demands), ii) realistic and holistic numerical models, iii) enhanced remote sensing and sensors, iv) expanded sample collection and retrieval technologies, and v) greater cyber-infrastructure to process ‘big data’ collection, transmission and analyses while promoting data accessibility. These technologies must be widely available, performance and reliability must be improved and technologies used elsewhere must be applied to the Antarctic. Considerable Antarctic research is field-based, making access to vital geographical targets essential. Future research will require continent- and ocean-wide environmentally responsible access to coastal and interior Antarctica and the Southern Ocean. Year-round access is indispensable. The cost of future Antarctic science is great but there are opportunities for all to participate commensurate with national resources, expertise and interests. The scope of future Antarctic research will necessitate enhanced and inventive interdisciplinary and international collaborations. The full promise of Antarctic science will only be realized if nations act together.
Roberts J, Curran M, Poynter S, et al., 2016, Correlation confidence limits for unevenly sampled data, Computers & Geosciences, Vol: 104, Pages: 120-124, ISSN: 0098-3004
Estimation of correlation with appropriate uncertainty limits for scientific data that are potentially serially correlated is a common problem made seriously challenging especially when data are sampled unevenly in space and/or time. Here we present a new, robust method for estimating correlation with uncertainty limits between autocorrelated series that does not require either resampling or interpolation. The technique employs the Gaussian kernel method with a bootstrapping resampling approach to derive the probability density function and resulting uncertainties. The method is validated using an example from radar geophysics. Autocorrelation and error bounds are estimated for an airborne radio-echo profile of ice sheet thickness. The computed limits are robust when withholding 10%, 20%, and 50% of data. As a further example, the method is applied to two time-series of methanesulphonic acid in Antarctic ice cores from different sites. We show how the method allows evaluation of the significance of correlation where the signal-to-noise ratio is low and reveals that the two ice cores exhibit a significant common signal.
Jordan T, Bamber J, Williams C, et al., 2016, An ice sheet wide framework for radar-inference of englacial attenuation and basal reflection with application to Greenland, Cryosphere, Vol: 10, Pages: 1547-1570, ISSN: 1994-0424
Radar inference of the bulk properties of glacierbeds, most notably identifying basal melting, is, in general,derived from the basal reflection coefficient. On the scale ofan ice sheet, unambiguous determination of basal reflectionis primarily limited by uncertainty in the englacial attenuationof the radio wave, which is an Arrhenius function oftemperature. Existing bed-returned power algorithms for derivingattenuation assume that the attenuation rate is regionallyconstant, which is not feasible at an ice-sheet-wide scale.Here we introduce a new semi-empirical framework for derivingenglacial attenuation, and, to demonstrate its efficacy,we apply it to the Greenland Ice Sheet. A central featureis the use of a prior Arrhenius temperature model to estimatethe spatial variation in englacial attenuation as a firstguess input for the radar algorithm. We demonstrate regionsof solution convergence for two input temperature fields andfor independently analysed field campaigns. The coverageachieved is a trade-off with uncertainty and we propose thatthe algorithm can be “tuned” for discrimination of basal melt(attenuation loss uncertainty ∼ 5 dB). This is supported byour physically realistic (∼ 20 dB) range for the basal reflectioncoefficient. Finally, we show that the attenuation solutioncan be used to predict the temperature bias of thermomechanicalice sheet models and is in agreement with known modeltemperature biases at the Dye 3 ice core.
Cooper MA, Michaelides K, Siegert MJ, et al., 2016, Paleofluvial landscape inheritance for Jakobshavn Isbræ catchment, Greenland, Geophysical Research Letters, Vol: 43, Pages: 6350-6357, ISSN: 1944-8007
Subglacial topography exerts strong controls on glacier dynamics, influencing the orientation and velocity of ice flow, as well as modulating the distribution of basal waters and sediment. Bed geometry can also provide a long-term record of geomorphic processes, allowing insight into landscape evolution, the origin of which may predate ice sheet inception. Here we present evidence from ice-penetrating radar data for a large dendritic drainage network, radiating inland from Jakobshavn Isbræ, Greenland's largest outlet glacier. The size of the drainage basin is ∼450,000 km2 and accounts for about 20% of the total land area of Greenland. Topographic and basin morphometric analyses of an isostatically uplifted (ice-free) bedrock topography suggests that this catchment predates ice sheet initiation and has likely been instrumental in controlling the location and form of the Jakobshavn ice stream, and ice flow from the deep interior to the margin, now and over several glacial cycles.
Aitken ARA, Roberts JL, van Ommen TD, et al., 2016, Repeated large-scale retreat and advance of Totten Glacier indicated by inland bed erosion, Nature, Vol: 533, Pages: 385-389, ISSN: 0028-0836
Siegert MJ, Ross N, Li J, et al., 2016, Subglacial controls on the flow of Institute Ice Stream, West Antarctica, Annals of Glaciology, Vol: 57, Pages: 19-24, ISSN: 1727-5644
The Institute Ice Stream (IIS) rests on a reverse-sloping bed, extending >150 km upstream into the ~1.8 km deep Robin Subglacial Basin, placing it at the threshold of marine ice-sheet instability. Understanding IIS vulnerability has focused on the effect of grounding-line melting, which is forecast to increase significantly this century. Changes to ice-flow dynamics are also important to IIS stability, yet little is known about them. Here we reveal the trunk of the IIS occurs downstream of the intersection of three discrete subglacial features; a large ‘active’ subglacial lake, a newly-discovered sharp transition to a zone of weak basal sediments, and a major tectonic rift. The border of IIS trunk flow is confined by the sediment on one side, and by a transition between basal melting and freezing at the border with the Bungenstock Ice Rise. By showing how basal sediment and water dictate present-day flow of IIS, we reveal that ice-sheet stability here is dependent on this unusual arrangement.
Siegert MJ, Frederick BC, Young DA, et al., 2016, Distribution of subglacial sediments across the Wilkes Subglacial Basin, East Antarctica, Journal of Geophysical Research. Earth Surface, Vol: 121, Pages: 790-813, ISSN: 2169-9003
Topography, sediment distribution, and heat flux are all key boundary conditions governing the dynamics of the East Antarctic Ice Sheet (EAIS). EAIS stability is most at risk in Wilkes Land across vast expanses of marine-based catchments including the 1400 km × 600 km expanse of the Wilkes Subglacial Basin (WSB) region. Data from a recent regional aerogeophysical survey (Investigating the Cryospheric Evolution of the Central Antarctic Plate (ICECAP)/IceBridge) are combined with two historical surveys (Wilkes basin/Transantarctic Mountains System Exploration-Ice-house Earth: Stability or DYNamism? (WISE-ISODYN) and Wilkes Land Transect (WLK)) to improve our understanding of the vast subglacial sedimentary basins impacting WSB ice flow and geomorphology across geologic time. Analyzing a combination of gravity, magnetic and ice-penetrating radar data, we present the first detailed subglacial sedimentary basin model for the WSB that defines distinct northern and southern subbasin isopachs with average sedimentary basin thicknesses of 1144 m ± 179 m and 1623 m ± 254 m, respectively. Notably, more substantial southern subbasin sedimentary deposition in the WSB interior supports a regional Wilkes Land hypothesis that basin-scale ice flow and associated glacial erosion is dictated by tectonic basement structure and the inherited geomorphology of preglacial fluvial networks. Orbital, temperate/polythermal glacial cycles emanating from adjacent alpine highlands during the early Miocene to late Oligocene likely preserved critical paleoclimatic data in subglacial sedimentary strata. Substantially thinner northern WSB subglacial sedimentary deposits are generally restricted to fault-controlled, channelized basins leading to prominent outlet glacier catchments suggesting a more dynamic EAIS during the Pliocene.
Siegert MJ, 2016, A wide variety of unique environments beneath the Antarcticice sheet, Geology, Vol: 44, Pages: 399-400, ISSN: 0091-7613
It is 20 years since subglacial Lake Vostok in central East Antarcticawas found to be one of the world’s largest freshwater bodies (Kapitsa et al.,1996). It was hypothesized to be both an ancient, extreme yet viable environmentfor microbial life, and a recorder of past climate change. Testingthese hypotheses is possible with direct measurement and sampling, butin-situ examination is challenging because of the thick ice to drill through,the necessary cleanliness required of the experiment, and the extremepolar conditions in which to operate. In this issue of Geology, Michaudet al. (2016, p. 347) report on water and sedimentary material collectedin January 2013 from Lake Whillans, a component of the hydrologicalsystem beneath Whillans ice stream in West Antarctica. They reveal thewater comprises melted basal ice and a small proportion of seawater, theconcentration of which increases with sediment depth, making it uniqueamong known subglacial environments within and outside of Antarctica.Here, to place the Lake Whillans work in context, I discuss the range ofAntarctic subglacial lake environments, showing the continent to containan assortment of systems in which novel physical, chemical, and biologicalprocesses may take place.
Cavitte M, Blankenship D, Young D, et al., 2016, Deep radiostratigraphy of the East Antarctic plateau: connectingthe Dome C and Vostok ice core sites, Journal of Glaciology, Vol: 62, Pages: 323-334, ISSN: 1727-5652
Several airborne radar-sounding surveys are used to trace internal reflections around theEuropean Project for Ice Coring in Antarctica Dome C and Vostok ice core sites. Thirteen reflections,spanning the last two glacial cycles, are traced within 200 km of Dome C, a promising region formillion-year-old ice, using the University of Texas Institute for Geophysics High-Capacity RadarSounder. This provides a dated stratigraphy to 2318 m depth at Dome C. Reflection age uncertaintiesare calculated from the radar range precision and signal-to-noise ratio of the internal reflections. Theradar stratigraphy matches well with the Multichannel Coherent Radar Depth Sounder (MCoRDS)radar stratigraphy obtained independently. We show that radar sounding enables the extension of icecore ages through the ice sheet with an additional radar-related age uncertainty of ∼1/3–1/2 that ofthe ice cores. Reflections are extended along the Byrd-Totten Glacier divide, using University ofTexas/Technical University of Denmark and MCoRDS surveys. However, core-to-core connection isimpeded by pervasive aeolian terranes, and Lake Vostok’s influence on reflection geometry. Poorradar connection of the two ice cores is attributed to these effects and suboptimal survey design inaffected areas. We demonstrate that, while ice sheet internal radar reflections are generally isochronaland can be mapped over large distances, careful survey planning is necessary to extend ice core chronologiesto distant regions of the East Antarctic ice sheet.
Siegert MJ, 2016, Environmental Sciences in the Twenty-First Century, Frontiers in Environmental Science, Vol: 4, ISSN: 2296-665X
Vance T, Roberts J, Moy A, et al., 2016, Optimal site selection for a high-resolution ice core record in East Antarctica, Climate of the Past, Vol: 12, Pages: 595-610, ISSN: 1814-9332
Ice cores provide some of the best-dated and most comprehensive proxy records, as they yield a vast and growing array of proxy indicators. Selecting a site for ice core drilling is nonetheless challenging, as the assessment of potential new sites needs to consider a variety of factors. Here, we demonstrate a systematic approach to site selection for a new East Antarctic high-resolution ice core record. Specifically, seven criteria are considered: (1) 2000-year-old ice at 300 m depth; (2) above 1000 m elevation; (3) a minimum accumulation rate of 250 mm years−1 IE (ice equivalent); (4) minimal surface reworking to preserve the deposited climate signal; (5) a site with minimal displacement or elevation change in ice at 300 m depth; (6) a strong teleconnection to midlatitude climate; and (7) an appropriately complementary relationship to the existing Law Dome record (a high-resolution record in East Antarctica). Once assessment of these physical characteristics identified promising regions, logistical considerations (for site access and ice core retrieval) were briefly considered. We use Antarctic surface mass balance syntheses, along with ground-truthing of satellite data by airborne radar surveys to produce all-of-Antarctica maps of surface roughness, age at specified depth, elevation and displacement change, and surface air temperature correlations to pinpoint promising locations. We also use the European Centre for Medium-Range Weather Forecast ERA 20th Century reanalysis (ERA-20C) to ensure that a site complementary to the Law Dome record is selected. We find three promising sites in the Indian Ocean sector of East Antarctica in the coastal zone from Enderby Land to the Ingrid Christensen Coast (50–100° E). Although we focus on East Antarctica for a new ice core site, the methodology is more generally applicable, and we include key parameters for all of Antarctica which may be useful for ice core site selection elsewhere and/or for other purposes.
Aitken ARA, Betts PG, Young DA, et al., 2016, The Australo-Antarctic Columbia to Gondwana transition, Gondwana Research, Vol: 29, Pages: 136-152, ISSN: 1342-937X
From the Mesoproterozoic to Cambrian, Australo-Antarctica was characterised by tectonic reconfiguration as part of the supercontinents Columbia, Rodinia and Gondwana. New tectonic knowledge of the Wilkes Land region of Antarctica allows Australo-Antarctic tectonic linkages to be resolved through reconstruction into ca. 160 Ma Gondwana. We also resolve 330 ± 30 km of sinistral strike-slip offset on the > 3000 km long Mundrabilla-Frost Shear Zone and 260 ± 20 km of dextral offset on the > 1000 km long Aurora Fault to reconstruct the ca. 1150 Ma geometry of Australo-Antarctica. Using this revised geometry, we derive the first model of the Columbia to Gondwana reconfiguration process that is geometrically constrained to ~ 100 km scale. In this model, early Mesoproterozoic tectonics is driven by two opposing subduction systems. A dominantly west-dipping subduction zone existed at the eastern margin of Australo-Antarctica until ca. 1.55–1.50 Ga. A predominantly east-dipping subduction zone operated at the western margin of the Mawson Craton from ca. 1.70 Ga to ca. 1.42 Ga. The latter caused gradual westwards motion and clockwise rotation of the Mawson Craton relative to the West and North Australian Craton and the accretion of a series of continental ribbons now preserved in the Musgrave Province and its southern extensions. A mid-Mesoproterozoic switch to predominantly west-dipping subduction beneath the West Australian Craton brought about the final closure of the Mawson Craton with the North and West Australian Craton along the Rodona-Totten Shear Zone. Convergence was achieved prior to 1.31 Ga, but final collision may not have occurred until ca. 1.29 Ga. Post-1.29 Ga intraplate activity involved prolonged high-temperature orogenesis from 1.22 to 1.12 Ga, and significant movement on the Mundrabilla-Frost Shear Zone between 1.13 and 1.09 Ga, perhaps in response to the assembly of Rodinia at ca. 1.1 Ga. The Australo-Antarctic Craton was amalgama
Jamieson SSR, Ross N, Greenbaum JS, et al., 2015, An extensive subglacial lake and canyon system in Princess Elizabeth Land, East Antarctica, Geology, Vol: 44, Pages: 87-90, ISSN: 1943-2682
The subglacial landscape of Princess Elizabeth Land (PEL) in East Antarctica is poorly known due to a paucity of ice thickness measurements. This is problematic given its importance for understanding ice sheet dynamics and landscape and climate evolution. To address this issue, we describe the topography beneath the ice sheet by assuming that ice surface expressions in satellite imagery relate to large-scale subglacial features. We find evidence that a large, previously undiscovered subglacial drainage network is hidden beneath the ice sheet in PEL. We interpret a discrete feature that is 140 × 20 km in plan form, and multiple narrow sinuous features that extend over a distance of ∼1100 km. We hypothesize that these are tectonically controlled and relate to a large subglacial basin containing a deep-water lake in the interior of PEL linked to a series of long, deep canyons. The presence of 1-km-deep canyons is confirmed at a few localities by radio-echo sounding data, and drainage analysis suggests that these canyons will direct subglacial meltwater to the coast between the Vestfold Hills and the West Ice Shelf.
Pearce DA, Magiopoulos I, Mowlem M, et al., 2015, Microbiology: lessons from a first attempt at Lake Ellsworth, Philosophical Transactions A: Mathematical, Physical and Engineering Sciences, Vol: 374, ISSN: 1364-503X
During the attempt to directly access, measure and sample Subglacial Lake Ellsworth in 2012–2013, we conducted microbiological analyses of the drilling equipment, scientific instrumentation, field camp and natural surroundings. From these studies, a number of lessons can be learned about the cleanliness of deep Antarctic subglacial lake access leading to, in particular, knowledge of the limitations of some of the most basic relevant microbiological principles. Here, we focus on five of the core challenges faced and describe how cleanliness and sterilization were implemented in the field. In the light of our field experiences, we consider how effective these actions were, and what can be learnt for future subglacial exploration missions. The five areas covered are: (i) field camp environment and activities, (ii) the engineering processes surrounding the hot water drilling, (iii) sample handling, including recovery, stability and preservation, (iv) clean access methodologies and removal of sample material, and (v) the biodiversity and distribution of bacteria around the Antarctic. Comparisons are made between the microbiology of the Lake Ellsworth field site and other Antarctic systems, including the lakes on Signy Island, and on the Antarctic Peninsula at Lake Hodgson. Ongoing research to better define and characterize the behaviour of natural and introduced microbial populations in response to deep-ice drilling is also discussed. We recommend that future access programmes: (i) assess each specific local environment in enhanced detail due to the potential for local contamination, (ii) consider the sterility of the access in more detail, specifically focusing on single cell colonization and the introduction of new species through contamination of pre-existing microbial communities, (iii) consider experimental bias in methodological approaches, (iv) undertake in situ biodiversity detection to mitigate risk of non-sample return and post-sample contamination, and (
Ross N, Le Brocq AM, Siegert MJ, 2015, Recent advances in understanding Antarctic subglacial lakes and hydrology, Journal: Philosophical Transactions A: Mathematical, Physical and Engineering Sciences, Vol: 374, ISSN: 1471-2962
It is now well documented that over 400 subglacial lakes exist across the bed of the Antarctic Ice Sheet. They comprise a variety of sizes and volumes (from the approx. 250 km long Lake Vostok to bodies of water less than 1 km in length), relate to a number of discrete topographic settings (from those contained within valleys to lakes that reside in broad flat terrain) and exhibit a range of dynamic behaviours (from ‘active’ lakes that periodically outburst some or all of their water to those isolated hydrologically for millions of years). Here we critique recent advances in our understanding of subglacial lakes, in particular since the last inventory in 2012. We show that within 3 years our knowledge of the hydrological processes at the ice-sheet base has advanced considerably. We describe evidence for further ‘active’ subglacial lakes, based on satellite observation of ice-surface changes, and discuss why detection of many ‘active’ lakes is not resolved in traditional radio-echo sounding methods. We go on to review evidence for large-scale subglacial water flow in Antarctica, including the discovery of ancient channels developed by former hydrological processes. We end by predicting areas where future discoveries may be possible, including the detection, measurement and significance of groundwater (i.e. water held beneath the ice-bed interface).
Hodgson DA, Bentley MJ, Smith JA, et al., 2015, Technologies for retrieving sediment cores in Antarctic subglacial settings, Journal: Philosophical Transactions A: Mathematical, Physical and Engineering Sciences, Vol: 374, ISSN: 1471-2962
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.
Siegert MJ, Priscu JC, Alekhina IA, et al., 2015, Antarctic subglacial lake exploration: first results and future plans, Journal: Philosophical Transactions A: Mathematical, Physical and Engineering Sciences, Vol: 374, ISSN: 1471-2962
After more than a decade of planning, three attempts were made in 2012–2013 to access, measure in situ properties and directly sample subglacial Antarctic lake environments. First, Russian scientists drilled into the top of Lake Vostok, allowing lake water to infiltrate, and freeze within, the lower part of the ice-core borehole, from which further coring would recover a frozen sample of surface lake water. Second, UK engineers tried unsuccessfully to deploy a clean-access hot-water drill, to sample the water column and sediments of subglacial Lake Ellsworth. Third, a US mission successfully drilled cleanly into subglacial Lake Whillans, a shallow hydraulically active lake at the coastal margin of West Antarctica, obtaining samples that would later be used to prove the existence of microbial life and active biogeochemical cycling beneath the ice sheet. This article summarizes the results of these programmes in terms of the scientific results obtained, the operational knowledge gained and the engineering challenges revealed, to collate what is known about Antarctic subglacial environments and how to explore them in future. While results from Lake Whillans testify to subglacial lakes as being viable biological habitats, the engineering challenges to explore deeper more isolated lakes where unique microorganisms and climate records may be found, as exemplified in the Lake Ellsworth and Vostok missions, are considerable. Through international cooperation, and by using equipment and knowledge of the existing subglacial lake exploration programmes, it is possible that such environments could be explored thoroughly, and at numerous sites, in the near future.
Makinson K, Pearce D, Hodgson DA, et al., 2015, Clean subglacial access: prospects for future deep hot-water drilling, Philosophical Transactions A: Mathematical, Physical and Engineering Sciences, Vol: 374, ISSN: 1471-2962
Accessing and sampling subglacial environments deep beneath the Antarctic Ice Sheet presents several challenges to existing drilling technologies. With over half of the ice sheet believed to be resting on a wet bed, drilling down to this environment must conform to international agreements on environmental stewardship and protection, making clean hot-water drilling the most viable option. Such a drill, and its water recovery system, must be capable of accessing significantly greater ice depths than previous hot-water drills, and remain fully operational after connecting with the basal hydrological system. The Subglacial Lake Ellsworth (SLE) project developed a comprehensive plan for deep (greater than 3000 m) subglacial lake research, involving the design and development of a clean deep-ice hot-water drill. However, during fieldwork in December 2012 drilling was halted after a succession of equipment issues culminated in a failure to link with a subsurface cavity and abandonment of the access holes. The lessons learned from this experience are presented here. Combining knowledge gained from these lessons with experience from other hot-water drilling programmes, and recent field testing, we describe the most viable technical options and operational procedures for future clean entry into SLE and other deep subglacial access targets.
Winter K, Woodward J, Ross N, et al., 2015, Airborne radar evidence for tributary flow switching in Institute Ice Stream, West Antarctica: Implications for ice sheet configuration and dynamics, Journal of Geophysical Research: Earth Surface, Vol: 120, Pages: 1611-1625, ISSN: 2169-9011
Despite the importance of ice streaming to the evaluation of West Antarctic Ice Sheet (WAIS) stability we know little about mid- to long-term dynamic changes within the Institute Ice Stream (IIS) catchment. Here we use airborne radio echo sounding to investigate the subglacial topography, internal stratigraphy, and Holocene flow regime of the upper IIS catchment near the Ellsworth Mountains. Internal layer buckling within three discrete, topographically confined tributaries, through Ellsworth, Independence, and Horseshoe Valley Troughs, provides evidence for former enhanced ice sheet flow. We suggest that enhanced ice flow through Independence and Ellsworth Troughs, during the mid-Holocene to late Holocene, was the source of ice streaming over the region now occupied by the slow-flowing Bungenstock Ice Rise. Although buckled layers also exist within the slow-flowing ice of Horseshoe Valley Trough, a thicker sequence of surface-conformable layers in the upper ice column suggests slowdown more than ~4000 years ago, so we do not attribute enhanced flow switch-off here, to the late Holocene ice-flow reorganization. Intensely buckled englacial layers within Horseshoe Valley and Independence Troughs cannot be accounted for under present-day flow speeds. The dynamic nature of ice flow in IIS and its tributaries suggests that recent ice stream switching and mass changes in the Siple Coast and Amundsen Sea sectors are not unique to these sectors, that they may have been regular during the Holocene and may characterize the decline of the WAIS.
Bingham RG, Rippin DM, Karlsson NB, et al., 2015, Ice-flow structure and ice dynamic changes in the Weddell Sea sector of West Antarctica from radar-imaged internal layering, JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE, Vol: 120, Pages: 655-670, ISSN: 2169-9003
Greenbaum JS, Blankenship DD, Young DA, et al., 2015, Ocean access to a cavity beneath Totten Glacier in East Antarctica, NATURE GEOSCIENCE, Vol: 8, Pages: 294-298, ISSN: 1752-0894
Young DA, Lindzey LE, Blankenship DD, et al., 2015, Land-ice elevation changes from photon-counting swath altimetry: first applications over the Antarctic ice sheet, Journal of Glaciology, Vol: 61, Pages: 17-28, ISSN: 1727-5652
Satellite altimetric time series allow high-precision monitoring of ice-sheet mass balance.Understanding elevation changes in these regions is important because outlet glaciers along ice-sheetmargins are critical in controlling flow of inland ice. Here we discuss a new airborne altimetry datasetcollected as part of the ICECAP (International Collaborative Exploration of the Cryosphere by AirborneProfiling) project over East Antarctica. Using the ALAMO (Airborne Laser Altimeter with MappingOptics) system of a scanning photon-counting lidar combined with a laser altimeter, we extend the2003–09 surface elevation record of NASA’s ICESat satellite, by determining cross-track slope and thusindependently correcting for ICESat’s cross-track pointing errors. In areas of high slope, cross-trackerrors result in measured elevation change that combines surface slope and the actual z=t signal.Slope corrections are particularly important in coastal ice streams, which often exhibit both rapidlychanging elevations and high surface slopes. As a test case (assuming that surface slopes do not changesignificantly) we observe a lack of ice dynamic change at Cook Ice Shelf, while significant thinningoccurred at Totten and Denman Glaciers during 2003–09.
Kennicutt MC, Chown SL, Cassano JJ, et al., 2015, A roadmap for Antarctic and Southern Ocean science for the next two decades and beyond, Antarctic Science, Vol: 27, Pages: 3-18, ISSN: 1365-2079
Antarctic and Southern Ocean science is vital to understanding natural variability, the processesthat govern global change and the role of humans in the Earth and climate system. The potential for newknowledge to be gained from future Antarctic science is substantial. Therefore, the international Antarcticcommunity came together to ‘scan the horizon’ to identify the highest priority scientific questions thatresearchers should aspire to answer in the next two decades and beyond. Wide consultation was afundamental principle for the development of a collective, international view of the most important futuredirections in Antarctic science. From the many possibilities, the horizon scan identified 80 key scientificquestions through structured debate, discussion, revision and voting. Questions were clustered into seventopics: i) Antarctic atmosphere and global connections, ii) Southern Ocean and sea ice in a warming world,iii) ice sheet and sea level, iv) the dynamic Earth, v) life on the precipice, vi) near-Earth space and beyond,and vii) human presence in Antarctica. Answering the questions identified by the horizon scan will requireinnovative experimental designs, novel applications of technology, invention of next-generation field andlaboratory approaches, and expanded observing systems and networks. Unbiased, non-contaminatingprocedures will be required to retrieve the requisite air, biota, sediment, rock, ice and water samples.Sustained year-round access to Antarctica and the Southern Ocean will be essential to increase winter-timemeasurements. Improved models are needed that represent Antarctica and the Southern Ocean in theEarth System, and provide predictions at spatial and temporal resolutions useful for decision making.A co-ordinated portfolio of cross-disciplinary science, based on new models of international collaboration,will be essential as no scientist, programme or nation can realize these aspirations alone.
Rose KC, Ross N, Jordan TA, et al., 2015, Ancient pre-glacial erosion surfaces preserved beneath the West Antarctic Ice Sheet, EARTH SURFACE DYNAMICS, Vol: 3, Pages: 139-152, ISSN: 2196-6311
Rose KC, Ross N, Bingham RG, et al., 2014, A temperate former West Antarctic ice sheet suggested by an extensive zone of subglacial meltwater channels, Geology, Vol: 42, Pages: 971-974, ISSN: 0091-7613
Several recent studies predict that the West Antarctic Ice Sheet will become increasingly unstable under warmer conditions. Insights on such change can be assisted through investigations of the subglacial landscape, which contains imprints of former ice-sheet behavior. Here, we present radio-echo sounding data and satellite imagery revealing a series of ancient large sub-parallel subglacial bed channels preserved in the region between the Möller and Foundation Ice Streams, West Antarctica. We suggest that these newly recognized channels were formed by significant meltwater routed along the icesheet bed. The volume of water required is likely substantial and can most easily be explained by water generated at the ice surface. The Greenland Ice Sheet today exemplifies how significant seasonal surface melt can be transferred to the bed via englacial routing. For West Antarctica, the Pliocene (2.6–5.3 Ma) represents the most recent sustained period when temperatures could have been high enough to generate surface melt comparable to that of present-day Greenland. We propose, therefore, that a temperate ice sheet covered this location during Pliocene warm periods.
Kennicutt MC, Chown SL, Cassano JJ, et al., 2014, Polar Research: Six priorities for Antarctic science, NATURE, Vol: 512, Pages: 23-25, ISSN: 0028-0836
Rippin DM, Bingham RG, Jordan TA, et al., 2014, Basal roughness of the Institute and Moller Ice Streams, West Antarctica: Process determination and landscape interpretation, GEOMORPHOLOGY, Vol: 214, Pages: 139-147, ISSN: 0169-555X
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