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Provenance records from sediments deposited offshore of the West Antarctic Ice Sheet (WAIS) can help identify past major ice retreat, thus constraining ice-sheet models projecting future sea-level rise. Interpretations from such records are, however, hampered by the ice obscuring Antarctica's geology. Here, we explore central West Antarctica's subglacial geology using basal debris from within the Byrd ice core, drilled to the bed in 1968. Sand grain microtextures and a high kaolinite content (∼38–42%) reveal the debris consists predominantly of eroded sedimentary detritus, likely deposited initially in a warm, pre-Oligocene, subaerial environment. Detrital hornblende 40Ar/39Ar ages suggest proximal late Cenozoic subglacial volcanism. The debris has a distinct provenance signature, with: common Permian-Early Jurassic mineral grains; absent early Ross Orogeny grains; a high kaolinite content; and high 143Nd/144Nd and low 87Sr/86Sr ratios. Detecting this “fingerprint” in Antarctic sedimentary records could imply major WAIS retreat, revealing the WAIS's sensitivity to future warming.

Knowledge of Antarctica’s sedimentary basins builds our understanding of the coupled evolution of tectonics, ice, ocean, and climate. Sedimentary basins have properties distinct from basement-dominated regions that impact ice-sheet dynamics, potentially influencing future ice-sheet change. Despite their importance, our knowledge of Antarctic sedimentary basins is restricted. Remoteness, the harsh environment, the overlying ice sheet, ice shelves and sea ice all make fieldwork challenging. Nonetheless, in the past decade the geophysics community has made great progress in internationally coordinated data collection and compilation with parallel advances in data processing and analysis supporting a new insight into Antarctica’s subglacial environment. Here, we summarize recent progress in understanding Antarctica’s sedimentary basins. We review advances in the technical capability of radar, potential fields, seismic and electromagnetic techniques to detect and characterize basins beneath ice and advances in integrated multi-data interpretation including machine-learning approaches. These new capabilities permit a continent-wide mapping of Antarctica’s sedimentary basins and their characteristics, aiding definition of the tectonic development of the continent. Crucially, Antarctica’s sedimentary basins interact with the overlying ice sheet through dynamic feedbacks that have the potential to contribute to rapid ice-sheet change. Looking ahead, future research directions include techniques to increase data coverage within logistical constraints, and resolving major knowledge gaps, including insufficient sampling of the ice-sheet bed and poor definition of subglacial basin structure and stratigraphy. Translating the knowledge of sedimentary basin processes into ice-sheet modelling studies is critical to underpin better capacity to predict future change.

Early to Middle Miocene sea-level oscillations of approximately 40-60 m estimated from far-field records(1-3) are interpreted to reflect the loss of virtually all East Antarctic ice during peak warmth(2). This contrasts with ice-sheet model experiments suggesting most terrestrial ice in East Antarctica was retained even during the warmest intervals of the Middle Miocene(4,5). Data and model outputs can be reconciled if a large West Antarctic Ice Sheet (WAIS) existed and expanded across most of the outer continental shelf during the Early Miocene, accounting for maximum ice-sheet volumes. Here weprovide the earliest geological evidence proving large WAIS expansions occurred during the Early Miocene (similar to 17.72-17.40 Ma). Geochemical and petrographic data show glacimarine sediments recovered at International Ocean Discovery Program (IODP) Site U1521 in the central Ross Sea derive from West Antarctica, requiring the presence of a WAIS covering most of the Ross Sea continental shelf. Seismic, lithological and palynological data reveal the intermittent proximity of grounded ice to Site U1521. The erosion rate calculated from this sediment package greatly exceeds the long-term mean, implying rapid erosion of West Antarctica. This interval therefore captures akey step in the genesis of a marine-based WAIS and a tipping point in Antarctic ice-sheet evolution.

Is groundwater abundant in Antarctica and does it modulate ice flow? Answering this question matters because ice streams flow by gliding over a wet substrate of till. Water fed to ice-stream beds thus influences ice-sheet dynamics and, potentially, sea-level rise. It is recognized that both till and the sedimentary basins from which it originates are porous and could host a reservoir of mobile groundwater that interacts with the subglacial interfacial system. According to recent numerical modelling, up to half of all water available for basal lubrication, and time lags between hydrological forcing and ice-sheet response as long as millennia, may have been overlooked in models of ice flow. Here, we review evidence in support of Antarctic groundwater and propose how it can be measured to ascertain the extent to which it modulates ice flow. We present new seismoelectric soundings of subglacial till, and magnetotelluric and transient electromagnetic forward models of subglacial groundwater reservoirs. We demonstrate that multifaceted and integrated geophysical datasets can detect, delineate and quantify the groundwater contents of subglacial sedimentary basins and, potentially, monitor groundwater exchange rates between subglacial till layers. The paper thus describes a new area of glaciological investigation and how it should progress in future.

We present two narratives on the future of Antarctica and the Southern Ocean, from the perspective of an observer looking back from 2070. In the first scenario, greenhouse gas emissions remained unchecked, the climate continued to warm, and the policy response was ineffective; this had large ramifications in Antarctica and the Southern Ocean, with worldwide impacts. In the second scenario, ambitious action was taken to limit greenhouse gas emissions and to establish policies that reduced anthropogenic pressure on the environment, slowing the rate of change in Antarctica. Choices made in the next decade will determine what trajectory is realized.

Long-range airborne geophysical measurements were carried out in the ICEGRAV campaigns, covering hitherto unexplored parts of interior East Antarctica and part of the Antarctic Peninsula. The airborne surveys provided a regional coverage of gravity, magnetic and ice-penetrating radar measurements for major Dronning Maud Land ice stream systems, from the grounding lines up to the Recovery Lakes drainage basin, and filled in major data voids in Antarctic data compilations, such as AntGP for gravity data, ADMAP for magnetic data and BEDMAP2 for ice thickness data and the sub-ice topography. We present the first maps of gravity, magnetic and ice thickness data and bedrock topography for the region and show examples of bedrock topography and basal reflectivity patterns. The 2013 Recovery Lakes campaign was carried out with a British Antarctic Survey Twin Otter aircraft operating from the Halley and Belgrano II stations, as well as a remote field camp located at the Recovery subglacial Lake B site. Gravity measurements were the primary driver for the survey, with two airborne gravimeters (Lacoste and Romberg and Chekan-AM) providing measurements at an accuracy level of around 2 mGal r.m.s., supplementing GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) satellite data and confirming an excellent sub-milligal agreement between satellite and airborne data at longer wavelengths.

Ice cores in Antarctica and Greenland reveal ice-crystal fabrics that can be softer under simple shear compared with isotropic ice. Owing to the sparseness of ice cores in regions away from the ice divide, we currently lack information about the spatial distribution of ice fabrics and its association with ice flow. Radio-wave reflections are influenced by ice-crystal alignments, allowing them to be tracked provided reflections are recorded simultaneously in orthogonal orientations (polarimetric measurements). Here, we image spatial variations in the thickness and extent of ice fabric across Dome A in East Antarctica, by interpreting polarimetric radar data. We identify four prominent fabric units, each several hundred metres thick, extending over hundreds of square kilometres. By tracing internal ice-sheet layering to the Vostok ice core, we are able to determine the approximate depth–age profile at Dome A. The fabric units correlate with glacial–interglacial cycles, most noticeably revealing crystal alignment contrasts between the Eemian and the glacial episodes before and after. The anisotropy within these fabric layers has a spatial pattern determined by ice flow over subglacial topography.

Although the flow of the East Antarctic Ice Sheet is well constrained from surface measurements and altimetry, our knowledge of the dynamic processes within the ice sheet remains limited. Recent high-resolution radar data from the Gamburtsev Subglacial Mountains in central East Antarctica reveal a series of anomalous englacial reflectors in the lower half of the ice column that cannot be explained by conventional ice flow. Expanding on previous analyses, we describe the geometrical and morphological features of 12 of these anomalous reflectors. Our description reveals a previously unacknowledged diversity in size, geometry and internal structure of these reflectors. We are able to identify four distinct morphological features: (1) fingers; (2) inclusions; (3) sheets; and (4) folds. The ‘fingers’ and ‘inclusions’ probably form by shear instabilities at the boundary between the reflectors and the surrounding meteoric ice. The ‘sheets’ highlight that basal ice can be uplifted off of the bed and above surrounding meteoric ice, and the ‘folds’ may have formed in local regions of converging flow associated with subglacial topography. The study provides key insights into the rheology, stress and deformational regimes deep within the central East Antarctic Ice Sheet.

The Institute Ice Stream (IIS) in West Antarctica may be increasingly vulnerable to melting at the grounding line through modifications in ocean circulation. Understanding such change requires knowledge of grounding-line boundary conditions, including the topography on which it rests. Here, we discuss evidence from new radio-echo sounding (RES) data on the subglacial topography adjacent to the grounding line of the IIS. In doing so, we reveal a previously unknown subglacial embayment immediately inland of the IIS grounding zone which is not represented in the Bedmap2 compilation. We discuss whether there is an open-water connection between the embayment and the ice-shelf cavity. The exact location of the grounding line over the embayment has been the subject of considerable uncertainty, with several positions being proposed recently. From our compilation of data, we are able to explain which of these grounding lines is most likely and, in doing so, highlight the need for accurate bed topography in conjunction with satellite observations to fully comprehend ice-sheet processes in this region and other vulnerable locations at the grounded margin of Antarctica.

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.

Antarctic and Southern Ocean science is vital to understanding natural variability, the processes that govern global change and the role of humans in the Earth and climate system. The potential for new knowledge to be gained from future Antarctic science is substantial. Therefore, the international Antarctic community came together to ‘scan the horizon’ to identify the highest priority scientific questions that researchers should aspire to answer in the next two decades and beyond. Wide consultation was a fundamental principle for the development of a collective, international view of the most important future directions in Antarctic science. From the many possibilities, the horizon scan identified 80 key scientific questions through structured debate, discussion, revision and voting. Questions were clustered into seven topics: 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 require innovative experimental designs, novel applications of technology, invention of next-generation field and laboratory approaches, and expanded observing systems and networks. Unbiased, non-contaminating procedures 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-time measurements. Improved models are needed that represent Antarctica and the Southern Ocean in the Earth 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.

Wilkes Land is a key region for studying the configuration of Gondwana and for appreciating the role of tectonic boundary conditions on East Antarctic Ice Sheet (EAIS) behavior. Despite this importance, it remains one of the largest regions on Earth where we lack a basic knowledge of geology. New magnetic, gravity and subglacial topography data allow the region's first comprehensive geological interpretation. We map lithospheric domains and their bounding faults, including the suture between Indo-Antarctica and Australo-Antarctica. Furthermore, we image subglacial sedimentary basins, including the Aurora and Knox Subglacial Basins, and the previously unknown Sabrina Subglacial Basin. Commonality of structure in magnetic, gravity and topography data suggest that pre-EAIS tectonic features are a primary control on subglacial topography. The preservation of this relationship after glaciation suggests that these tectonic features provide topographic and basal boundary conditions that have strongly influenced the structure and evolution of the EAIS.

A recent ocean modelling study indicates that possible changes in circulation may bring warm deep-ocean water into direct contact with the grounding lines of the Filchner–Ronne ice streams, suggesting the potential for future ice losses from this sector equivalent to ~0.3 m of sea-level rise. Significant advancements have been made in our knowledge of both the basal topography and ice velocity in the Weddell Sea sector, and the ability to accurately model marine ice sheet dynamics, thus enabling an assessment to be made of the relative sensitivities of the diverse collection of ice streams feeding the Filchner–Ronne Ice Shelf. Here we use the BISICLES ice sheet model, which employs adaptive-mesh refinement to resolve grounding line dynamics, to carry out such an assessment. The impact of realistic perturbations to the surface and sub-shelf mass balance forcing fields from our 2000-year "reference" model run indicate that both the Institute and Möller ice streams are highly sensitive to changes in basal melting either near to their respective grounding lines, or in the region of the ice rises within the Filchner–Ronne Ice Shelf. These same perturbations have little impact, however, on the Rutford, Carlson or Foundation ice streams, while the Evans Ice Stream is found to enter a phase of unstable retreat only after melt at its grounding line has increased by 50% of likely present-day values.

Antarctic and Southern Ocean science is vital to understanding natural variability, the processes that govern global change and the role of humans in the Earth and climate system. The potential for new knowledge to be gained from future Antarctic science is substantial. Therefore, the international Antarctic community came together to ‘scan the horizon’ to identify the highest priority scientific questions that researchers should aspire to answer in the next two decades and beyond. Wide consultation was a fundamental principle for the development of a collective, international view of the most important future directions in Antarctic science. From the many possibilities, the horizon scan identified 80 key scientific questions through structured debate, discussion, revision and voting. Questions were clustered into seven topics: 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 require innovative experimental designs, novel applications of technology, invention of next-generation field and laboratory approaches, and expanded observing systems and networks. Unbiased, non-contaminating procedures will be required to retrieve the requisite air, biota, sediment, rock, ice and water samples. Sustained year-round access toAntarctica and the Southern Ocean will be essential to increase winter-time measurements. Improved models are needed that represent Antarctica and the Southern Ocean in the Earth 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.

Meltwater generated beneath the Antarctic Ice Sheet exerts a strong influence on the speed of ice flow, in particular for major ice streams1, 2. The subglacial meltwater also influences ocean circulation beneath ice shelves, initiating meltwater plumes that entrain warmer ocean water and cause high rates of melting3. However, despite its importance, the nature of the hydrological system beneath the grounded ice sheet remains poorly characterized. Here we present evidence, from satellite and airborne remote sensing, for large channels beneath the floating Filchner–Ronne Ice Shelf in West Antarctica, which we propose provide a means for investigating the hydrological system beneath the grounded ice sheet. We observe features on the surface of the ice shelf from satellite imagery and, using radar measurements, show that they correspond with channels beneath the ice shelf. We also show that the sub-ice-shelf channels are aligned with locations where the outflow of subglacial meltwater has been predicted. This agreement indicates that the sub-ice-shelf channels are formed by meltwater plumes, initiated by subglacial water exiting the upstream grounded ice sheet in a focused (channelized) manner. The existence of a channelized hydrological system has implications for the behaviour and dynamics of ice sheets and ice shelves near the grounding lines of ice streams in Antarctica.

We present Bedmap2, a new suite of gridded products describing surface elevation, ice-thickness and the seafloor and subglacial bed elevation of the Antarctic south of 60° S. We derived these products using data from a variety of sources, including many substantial surveys completed since the original Bedmap compilation (Bedmap1) in 2001. In particular, the Bedmap2 ice thickness grid is made from 25 million measurements, over two orders of magnitude more than were used in Bedmap1. In most parts of Antarctica the subglacial landscape is visible in much greater detail than was previously available and the improved data-coverage has in many areas revealed the full scale of mountain ranges, valleys, basins and troughs, only fragments of which were previously indicated in local surveys. The derived statistics for Bedmap2 show that the volume of ice contained in the Antarctic ice sheet (27 million km3) and its potential contribution to sea-level rise (58 m) are similar to those of Bedmap1, but the mean thickness of the ice sheet is 4.6% greater, the mean depth of the bed beneath the grounded ice sheet is 72 m lower and the area of ice sheet grounded on bed below sea level is increased by 10%. The Bedmap2 compilation highlights several areas beneath the ice sheet where the bed elevation is substantially lower than the deepest bed indicated by Bedmap1. These products, along with grids of data coverage and uncertainty, provide new opportunities for detailed modelling of the past and future evolution of the Antarctic ice sheets.

The direct measurement and sampling of Ellsworth Subglacial Lake is a multidisciplinary investigation of life in extreme environments and West Antarctic ice sheet history. The project's aims are (1) to determine whether, and in what form, microbial life exists in Antarctic subglacial lakes and (2) to reveal the post-Pliocene history of the West Antarctic Ice Sheet. A U.K. consortium has planned an extensive logistics and equipment development program that will deliver the necessary resources. This will include hot water drill technology for lake access through approximately 3.2 km of ice, a probe to make measurements with sensors and to collect water and sediment samples, and a percussion corer to acquire an ˜3–4 m sediment core. This chapter details the requirements and early stages of design and development of the probe system. This includes the instrumentation package, water samplers, and a mini gravity corer mounted on the front of the probe. Initial design concepts for supporting equipment required at the drill site to deploy and operate the probe are also described. A review of the literature describing relevant technology is presented. The project will implement environmental protection in line with principles set out by the Scientific Committee on Antarctic Research.

Ellsworth Subglacial Lake, first observed in airborne radio echo sounding data acquired in 1978, is located within a long, deep subglacial trough within the Ellsworth Subglacial Highlands of West Antarctica. Geophysical surveys have characterized the lake, its subglacial catchment, and the thickness, structure, and flow of the overlying ice sheet. Covering 28.9 km2, Ellsworth Subglacial Lake is located below 2.9 to 3.3 km of ice at depths of −1361 to −1030 m. Seismic reflection data have shown the lake to be up to 156 m deep and underlain by unconsolidated sediments. Ice sheet flow over the lake is characterized by low velocities (<6 m yr−1), flow convergence, and longitudinal extension. The lake appears to be in steady state, although the hydrological balance may vary over glacial-interglacial cycles. Direct access, measurement, and sampling of Ellsworth Subglacial Lake are planned for the 2012/2013 Antarctic field season. The aims of this access experiment are to determine (1) the presence, character, and maintenance of microbial life in Antarctic subglacial lakes and (2) the Quaternary history of the West Antarctic ice sheet. Geophysical data have been used to define a preferred lake access site. The factors that make this location suitable for exploration are (1) a relatively thin overlying ice column (∼3.1 km), (2) a significant measured water depth (∼143 m), (3) >2 m of sediment below the lake floor, (4) water circulation modeling suggesting a melting ice-water interface, and (5) coring that can target the deepest point of the lake floor away from marginal, localized sediment sources.

We analyze Holocene ice flow using global positioning system and radio-echo sounding data acquired near the Amundsen-Weddell ice divide, between Pine Island Glacier and the Institute Ice Stream, West Antarctica. The data show that this part of the West Antarctic Ice Sheet (WAIS) has maintained a stable ice flow regime and ice divide position for similar to 7000 yr. Independent glacial geological data, in support of this assertion, suggest that the interior of the WAIS west of the Ellsworth Mountains has thinned by only a few hundred meters since the Last Glacial Maximum (LGM) and that the position of the ice divide may be recurrent over longer (more than 20 k.y., perhaps pre-Quaternary) time scales. We suggest that basal topography constrains ice flow in this sector of the WAIS, making the ice divide relatively insensitive to perturbations around the margins of the ice sheet compared with other ice divides. Large-scale forcing measured elsewhere in the WAIS as major reorganizations of the ice sheet surface and flowline pattern may be manifested only in simple vertical changes of the Amundsen-Weddell interior.

Continental margin drill core and seismic data indicate that between 3.0 and 2.5 Ma, high-latitude climate cooling drove both the West and East Antarctic Ice Sheets towards their present expanded cold polar state. Ice margins developed permanent marine termini with ice shelves. Direct physical sedimentary records of Antarctic Ice Sheet variability (e.g. ice-rafted debris, proximal glacimarine cycles) and more distal ocean records of sea-ice distribution (e.g. diatom palaeoecology), thermohaline circulation (e.g. sortable silt), ocean temperatures (e.g. δ18O), frontal dynamics and surface circulation (e.g. palaeoecological assemblages and sea-surface temperature (SST) reconstructions) all show a strong covariance with the 41 kyr cycle in Earth's obliquity between 3 and 1 Ma. Glacial periods are characterised by northward expansion of seasonal sea ice, SSTs up to 6°C colder than now, equatorward migration of frontal zones by 5–10° latitude, intensification of zonal westerly winds, invigorated surface circulation (e.g. Antarctic Circumpolar Current) and intensified abyssal currents. These processes lead the δ18O ice volume maximum by 3–7 kyr, at which time Antarctic Ice Sheets were fully extended onto the continental shelf. Antarctic ice volume changes were in part controlled by the effect of Northern Hemisphere glacio-eustasy on its marine margin, and this mechanism accounts for much of the orbital variability of the last 2.6 myr. An enigmatic interval of foraminiferal ooze and coccolith-bearing sediments in Weddell Sea and Prydz Bay sediment cores, together with a bioclastic limestone in the Ross Sea at 1 Ma, imply a significant warming and change in ocean chemistry around the periphery of Antarctica. This event, which occurs within the short normal polarity Jaramillo Subchron in Ross Sea cores, is correlated with warm Marine Isotope Stage 31. The anomalous warming implies an increase of 4–6°C in SST, possible incursion of Subantarctic Surface Waters and depression o

Seismic stratigraphic studies and scientific drilling of the Antarctic continental margin have yielded clues to the evolution of Cenozoic climates, depositional paleoenvironments and paleoceanographic conditions. This paper draws on studies of the former Antarctic Offshore Stratigraphy Project and others to review the geomorphic and lithostratigraphic offshore features that give insights into the long-duration (m.y.) and short-term (k.y.) changes that document the great variability of Cenozoic Antarctic paleoenvironments. The lithologic drilling record documents non-glacial (pre-early Eocene) to full-glacial (late Pliocene to Holocene) times, and documents times of cyclic ice-sheet fluctuations at k.y. scales (early Miocene to Pliocene and Holocene). Times of significant change in types and/or amounts of glaciation are also seen in the offshore lithologic record (early Oligocene, mid-Miocene, early Pliocene). Seismic data illustrate large-scale geomorphic features that point to massive sediment erosion and dispersal by ice sheets and paleoceanographic processes (e.g. cross-shelf troughs, slope-fans, rise-drifts). The commonality of these features to East and West Antarctica since late Eocene time points to a continent that has been intermittently covered, partially to completely, by glaciers and ice sheets. The greatest advances in our understanding of paleoenvironments and the processes that control them have been achieved from scientific drilling, and future progress depends on a continuation of such drilling.

This chapter explores the Middle Miocene to Pliocene terrestrial and marine records of Antarctica and the Southern Ocean. The structure of the chapter makes a clear distinction between terrestrial and marine records as well as proximal (on or around Antarctica) and more distal records (Southern Ocean). Particular geographical regions are identified that reflect the areas for which the majority of palaeoenvironmental and palaeoclimatic information exist. Specifically, the chapter addresses the terrestrial sedimentary and fjordal environments of the Transantarctic Mountains and Lambert Glacier region, the terrestrial fossil record of Antarctic climate, terrestrial environments of West Antarctica, and the marine records of the East Antarctic Ice Sheet (EAIS), the West Antarctic Ice Sheet (WAIS) and the Antarctic Peninsula Ice Sheet (APIS), as well as the marine record of the Southern Ocean. Previous and current studies focusing on modelling Middle Miocene to Pliocene climate, environments and ice sheets are discussed.

Variations in the depth of radar-detectable englacial layers (isochrones) are commonly used to assess past variability in accumulation rates, but little is known about the effect of internal and basal flow variations on isochrone deflections (e.g.bumps, troughs). In this paper, we show how the isochrones are affected by such variation using a three-dimensional flow model to investigate changes in the flow mode and in increased basal melting. We also investigate how transverse flows with lateral velocity gradients affect the development of isochrones. We use the model to visualize how such variations will be seen in radar lines which cross the flow direction. We show that in the presence of lateral gradients in the flow field we can produce bumps and troughs when viewed along transects perpendicular to the flow. The model results show that the influences of flow convergence, melting and changes in flow mode, when coupled together, affect isochrones over the whole depth of the ice sheet. Finally, changes in the near-surface layers cannot be solely attributed to spatial variation in the accumulation rate; there can also be a strong signal from changes in the flow mode.

Contains fulltext : 49858.pdf (publisher's version ) (Closed access), RATIONALE AND OBJECTIVES: Electronic learning (e-learning) may provide a means to enhance learning efficacy. However, introduction of e-learning often fails. We describe a strategy of how an e-learning curriculum was successfully implemented. MATERIALS AND METHODS:The curriculum was designed based on published evidence. It consists of self-directed learning, an online discussion forum, and discussion rounds. The e-content in nuclear medicine and radiotherapy was produced by the k-MED team of medical authors, web designers, and psychologists. The online courses were delivered via a dedicated learning management system. The e-content for diagnostic radiology and physics was provided as PDF/HTML script by the respective teachers who objected to participate in the k-MED project. The exam was taken online. Online evaluation of the curriculum by the students was taken at the end of the course. RESULTS: The new curriculum proved very effective. The time for the preparation for the clinical part of the radiology course could be reduced from 4 to 2 weeks. The students particularly enjoyed the self-directed learning. Although the material provided by k-MED received 90%-99% positive scores, the HTML and PDF scripts scored worse (13%-67% positive ratings). The positive results of the evaluation convinced the teachers responsible for physics and diagnostic radiology to participate in k-MED. CONCLUSIONS: As our example shows, new e-learning curricula can successfully be introduced. The strategy of implementation should be based on the existing evidence from the literature. The new curriculum helped to increase the efficacy of teaching and save time as the duration of the respective part of the course could be reduced by half.

Radio-echo sounding data are used to investigate bed roughness beneath the three enhanced-flow tributaries of Slessor Glacier, East Antarctica. Slow-moving inter-tributary areas are found to have rough beds, while the bed of the northernmost tributary is relatively smooth. A reconstruction of potential subglacial drainage routing indicates that water would be routed down this tributary, and investigations of basal topography following isostatic recovery reveal that the bed would have been below sea level in preglacial times, so marine sediments may have accumulated here. Together, these factors are further support for the dominance of basal motion in this tributary, reported elsewhere. Conversely, although the other two Slessor tributaries may have water routed beneath them, they would not have been below sea level before the growth of the ice sheet, so cannot be underlain by marine sediments. They are also found to be rough, and, within the range of uncertainties, it is likely that basal motion does not play a major role in the flow of these tributaries. Perhaps the most interesting area, however, is a deep trough where flow rates are currently low but the bed is as smooth as the northern Slessor trough. It is proposed that, although ice deformation currently dominates in this trough, basal motion may have occurred in the past, when the ice was thicker.

No abstract available

The Antarctic Climate Evolution (ACE) project is a new international research initiative to study the climate and glacial history of Antarctica by linking climate and ice sheet modeling studies with geophysical surveys and geological studies on and around the Antarctic continent (Fig. 1). The rationale for the ACE programme, outlined herein, was developed and refined, before, during and after the Antarctic Earth Science Symposium in Erice, Italy, in September 2001 (Cooper et al., 2002, Florindo et al., 2003).

An airborne radio-echo sounding campaign carried out in the upper reaches of Bailey Ice Stream and Slessor Glacier, in Coats Land, East Antarctica, has revealed that tributaries of enhanced flow lie within well-defined basal troughs and are separated from each other by bed highs. These new data indicate significant differences in ice thickness compared with those estimated in the Bedmap database. A numerical modeling study has revealed that driving stresses are high enough to account for flow by ice deformation alone in intertributary areas. Most flow in the enhanced flow tributaries of Slessor Glacier may also be explained by ice deformation alone. However, although ice deformation is also significant in the Bailey Ice Stream tributary, a large amount of basal motion is also required to fully explain flow velocities here. It is proposed that the trough in which Bailey tributary lies is sufficiently deep that marine sediments may have accumulated here in preglacial times. Along with water produced by geothermal heating, frictional heating, and through a reduction in the pressure melting point, basal motion may therefore be facilitated by the presence of a deformable, saturated till layer at the bed.