Publications
333 results found
Siegert MJ, Makinson K, Blake D, et al., 2014, An assessment of deep hot-water drilling as a means to undertake direct measurement and sampling of Antarctic subglacial lakes: experience and lessons learned from the Lake Ellsworth field season 2012/13, ANNALS OF GLACIOLOGY, Vol: 55, Pages: 59-73, ISSN: 0260-3055
Ross N, Jordan TA, Bingham RG, et al., 2014, The Ellsworth Subglacial Highlands: Inception and retreat of the West Antarctic Ice Sheet, GEOLOGICAL SOCIETY OF AMERICA BULLETIN, Vol: 126, Pages: 3-15, ISSN: 0016-7606
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- Citations: 37
Wright AP, Le Brocq AM, Cornford SL, et al., 2014, Sensitivity of the Weddell Sea sector ice streams to sub-shelf melting and surface accumulation, CRYOSPHERE, Vol: 8, Pages: 2119-2134, ISSN: 1994-0416
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- Citations: 31
Wright AP, Young DA, Bamber JL, et al., 2014, Subglacial hydrological connectivity within the Byrd Glacier catchment, East Antarctica, JOURNAL OF GLACIOLOGY, Vol: 60, Pages: 345-352, ISSN: 0022-1430
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- Citations: 16
Palmer SJ, Dowdeswell JA, Christoffersen P, et al., 2013, Greenland subglacial lakes detected by radar, GEOPHYSICAL RESEARCH LETTERS, Vol: 40, Pages: 6154-6159, ISSN: 0094-8276
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- Citations: 54
Le Brocq AM, Ross N, Griggs JA, et al., 2013, Evidence from ice shelves for channelized meltwater flow beneath the Antarctic Ice Sheet, NATURE GEOSCIENCE, Vol: 6, Pages: 945-948, ISSN: 1752-0894
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- Citations: 152
Siegert M, Ross N, Corr H, et al., 2013, Late Holocene ice-flow reconfiguration in the Weddell Sea sector of West Antarctica, Quaternary Science Reviews, Vol: 78, Pages: 98-107, ISSN: 0277-3791
Here we report Late Holocene ice sheet and grounding-line changes to the Weddell Sea sector of West Antarctica. Internal radio-echo layering within the Bungenstock Ice Rise, which comprises very slow-flowing ice separating the fast-flowing Institute and Möller ice streams, reveals ice deformed by former enhanced flow, overlain by un-deformed ice. The ice-rise surface is traversed by surface lineations explicable as diffuse ice-flow generated stripes, which thus capture the direction of flow immediately prior to the creation of the ice rise. The arrangement of internal layers can be explained by adjustment to the flow path of the Institute Ice Stream, during either a phase of ice sheet retreat not longer than ∼4000 years ago or by wholesale expansion of the grounding-line from an already retreated situation not sooner than ∼400 years ago. Some combination of these events, involving uplift of the ice rise bed during ice stream retreat and reorganisation, is also possible. Whichever the case, the implication is that the ice sheet upstream of the Bungenstock Ice Rise, which currently grounds over a >1.5 km deep basin has been, and therefore may be, susceptible to significant change.
Bamber JL, Siegert MJ, Griggs JA, et al., 2013, Paleofluvial Mega-Canyon Beneath the Central Greenland Ice Sheet, SCIENCE, Vol: 341, Pages: 997-999, ISSN: 0036-8075
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- Citations: 61
Siegert MJ, Popov S, Studinger M, 2013, Vostok Subglacial Lake: A Review of Geophysical Data Regarding Its Discovery and Topographic Setting, Antarctic Subglacial Aquatic Environments, Pages: 45-60, ISBN: 9780875904825
Vostok Subglacial Lake is the largest and best known sub-ice lake in Antarctica. The establishment of its water depth (>500 m) led to an appreciation that such environments may be habitats for life and could contain ancient records of ice sheet change, which catalyzed plans for exploration and research. Here we discuss geophysical data used to identify the lake and the likely physical, chemical, and biological processes that occur in it. The lake is more than 250 km long and around 80 km wide in one place. It lies beneath 4.2 to 3.7 km of ice and exists because background levels of geothermal heating are sufficient to warm the ice base to the pressure melting value. Seismic and gravity measurements show the lake has two distinct basins. The Vostok ice core extracted >200 m of ice accreted from the lake to the ice sheet base. Analysis of this ice has given valuable insights into the lake's biological and chemical setting. The inclination of the ice-water interface leads to differential basal melting in the north versus freezing in the south, which excites circulation and potential mixing of the water. The exact nature of circulation depends on hydrochemical properties, which are not known at this stage. The age of the subglacial lake is likely to be as old as the ice sheet (~14 Ma). The age of the water within the lake will be related to the age of the ice melting into it and the level of mixing. Rough estimates put that combined age as ~1 Ma.
Ross N, Siegert MJ, Rivera A, et al., 2013, Ellsworth Subglacial Lake, West Antarctica: A Review of Its History and Recent Field Campaigns, Antarctic Subglacial Aquatic Environments, Pages: 221-233, ISBN: 9780875904825
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.
Wright A, Siegert MJ, 2013, The Identification and Physiographical Setting of Antarctic Subglacial Lakes: An Update Based on Recent Discoveries, Antarctic Subglacial Aquatic Environments, Pages: 9-26, ISBN: 9780875904825
We investigate the glaciological and topographic setting of known Antarctic subglacial lakes following a previous assessment by Dowdeswell and Siegert (2002) based on the first inventory of 77 lakes. Procedures used to detect subglacial lakes are discussed, including radio echo sounding (RES) (which was first used to demonstrate the presence of subglacial lakes), surface topography, topographical changes, gravity measurements, and seismic investigations. Recent discoveries of subglacial lakes using these techniques are detailed, from which a revised new inventory of subglacial lakes is established, bringing the total number of known subglacial lakes to 387. Using this new inventory, we examine various controls on subglacial lakes, such as overlying ice thickness and position within the ice sheet and formulate frequency distributions for the entire subglacial lake population based on these (variable) controls. We show how the utility of RES in identifying subglacial lakes is spatially affected; lakes away from the ice divide are not easily detected by this technique, probably due to scattering at the ice sheet base. We show that subglacial lakes are widespread in Antarctica, and it is likely that many are connected within well-defined subglacial hydrological systems.
Kennicutt MC, Siegert MJ, 2013, Subglacial Aquatic Environments: A Focus of 21st Century Antarctic Science, Antarctic Subglacial Aquatic Environments, Pages: 1-7, ISBN: 9780875904825
In 1996, growing evidence suggested a massive lake of liquid water had pooled beneath the East Antarctic Ice Sheet. This feature became known as "Lake Vostok." Early on, two hypotheses were posed: the lake contained microbial life that had evolved over millions of years in isolation beneath the ice and lake sediments contained records of past climate change obtainable nowhere else in Antarctica. Many subglacial lakes, in a number of locales, have been identified, suggesting that studies at multiple locations will be needed to fully understand the importance of subglacial aquatic environments. As of 2010, more than 300 lakes have been identified; this will increase as surveys improve spatial coverage. Given the likely pristine nature of these environs and the low levels of microbial life expected, exploration must be done in a manner that causes minimal impact or contamination. It has been shown that many of these lakes are part of an active, sub-ice hydrological system that experiences rapid water flow events over time frames of months, weeks, and even days.Microbial life in subglacial environments has been inferred, and is expected, but it has yet to be directly confirmed by in situ sampling. Current understanding of subglacial environments is incomplete and will only be improved when these subglacial environments are entered and sampled, which is projected to occur in the next few years. This book synthesizes current understanding of subglacial environments and the plans for their exploration as a benchmark for future discoveries.
Cockell CS, Bagshaw E, Balme M, et al., 2013, Subglacial Environments and the Search for Life Beyond the Earth, Antarctic Subglacial Aquatic Environments, Pages: 129-148, ISBN: 9780875904825
One of the most remarkable discoveries resulting from the robotic and remote sensing exploration of space is the inferred presence of bodies of liquid water under ice deposits on other planetary bodies: extraterrestrial subglacial environments. Most prominent among these are the ice-covered ocean of the Jovian moon, Europa, and the Saturnian moon, Enceladus. On Mars, although there is no current evidence for subglacial liquid water today, conditions may have been more favorable for liquid water during periods of higher obliquity. Data on these extraterrestrial environments show that while they share similarities with some subglacial environments on the Earth, they are very different in their combined physicochemical conditions. Extraterrestrial environments may provide three new types of subglacial settings for study: (1) uninhabitable environments that are more extreme and life-limiting than terrestrial subglacial environments, (2) environments that are habitable but are uninhabited, which can be compared to similar biotically influenced subglacial environments on the Earth, and (3) environments with examples of life, which will provide new opportunities to investigate the interactions between a biota and glacial environments.
Mowlem MC, Tsaloglou MN, Waugh EM, et al., 2013, Probe Technology for the Direct Measurement and Sampling of Ellsworth Subglacial Lake, Antarctic Subglacial Aquatic Environments, Pages: 159-186, ISBN: 9780875904825
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.
Siegert M, Bradwell T, 2013, Antarctic Earth Sciences: Preface, EARTH AND ENVIRONMENTAL SCIENCE TRANSACTIONS OF THE ROYAL SOCIETY OF EDINBURGH, Vol: 104, Pages: 1-1, ISSN: 1755-6910
Jordan TA, Ferraccioli F, Ross N, et al., 2013, Inland extent of the Weddell Sea Rift imaged by new aerogeophysical data, TECTONOPHYSICS, Vol: 585, Pages: 137-160, ISSN: 0040-1951
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- Citations: 59
Cavitte MGP, Blankenship DD, Young DA, et al., 2013, Supplementary material to &quot;Radar stratigraphy connecting Lake Vostok and Dome C, East Antarctica, constrains the EPICA/DMC ice core time scale&quot;
Cavitte MGP, Blankenship DD, Young DA, et al., 2013, Radar stratigraphy connecting Lake Vostok and Dome C, East Antarctica, constrains the EPICA/DMC ice core time scale
<jats:p>Abstract. New airborne radar sounding surveys at 60 MHz are used to trace internal layering between the Vostok and EPICA Dome C ice core sites. Eleven layers, spanning two glacial cycles from the last glacial maximum back to the MIS 7c interglacial, are used to correlate the two ice core chronologies. Independent of palaeoclimate signals, radar sounding enables correlation of the timescales, with a radar depth uncertainty equivalent to hundreds of years, which is small relative to the ice core dating uncertainties of thousands of years. Along the radar transects, horizons belonging to the last glacial cycle are impacted by aeolian stratigraphic reworking that increases radar technique uncertainty for this interval. However, older layers are used to propagate the higher resolution Vostok ages to the lower resolution Dome C ice core using the Suwa and Bender (2008) Vostok O2 / N2 chronology to give a recalibration of the Parrenin et al. (2007) EPICA EDC3 timescale between 1597 m and 2216 m depth (126 ka to 247 ka age interval). </jats:p>
White J, Siegert M, 2013, One minute with ... Martin Siegert, NEW SCIENTIST, Vol: 217, Pages: 25-25, ISSN: 0262-4079
Siegert MJ, 2013, Growth and Decay, Encyclopedia of Quaternary Science: Second Edition, Pages: 877-883, ISBN: 9780444536426
The growth and decay cycle of ice sheets is forced by orbital variations of Earth around the Sun. Changes in solar inputs resulting from these variations are too small, however, to solely account for the expansion and retraction of huge ice masses. Instead, orbital climate forcing is supplemented by a series of positive feedback processes, which act to enhance climate cooling, resulting in large-scale glaciation. During deglaciation, as climate warms and ice sheets melt, feedback processes can act to speed up the decay of ice, which has been shown to result in short-term oscillations in climate conditions and, thus, ice sheet mass balance. Ice sheets grow first on land, as a response to climate cooling and the consequent lowering of equilibrium line altitudes. Such growth leads to changes in surface albedo (i.e., reflectivity of a surface, defined as the proportion of radiation reflected divided by the proportion of incoming radiation; hence, an albedo of 1 defines a surface with 100% reflectivity), atmospheric circulation, oceanic circulation and global sea level. Subsequently, shallow marine sections of continents may become glaciated when sea levels are close to their minimum. Ice sheet decay occurs first in lower latitudes and marine-based sections of ice sheets, leading to further sea-level rise. As deglaciation occurs, feedback may affect ice sheet breakup, resulting in accelerated decay and rapid short-term oscillations in ice sheet size.
Fretwell P, Pritchard HD, Vaughan DG, et al., 2013, Bedmap2: improved ice bed, surface and thickness datasets for Antarctica, CRYOSPHERE, Vol: 7, Pages: 375-393, ISSN: 1994-0416
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- Citations: 1327
Wright A, Siegert M, 2012, A fourth inventory of Antarctic subglacial lakes, ANTARCTIC SCIENCE, Vol: 24, Pages: 659-664, ISSN: 0954-1020
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- Citations: 152
Siegert M, 2012, Hunt for life under Antarctic ice heats up (vol 491, pg 506, 2012), NATURE, Vol: 491, Pages: 651-651, ISSN: 0028-0836
Ross N, Bingham RG, Corr HFJ, et al., 2012, Steep reverse bed slope at the grounding line of the Weddell Sea sector in West Antarctica, NATURE GEOSCIENCE, Vol: 5, Pages: 393-396, ISSN: 1752-0894
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- Citations: 91
Wright AP, Young DA, Roberts JL, et al., 2012, Evidence of a hydrological connection between the ice divide and ice sheet margin in the Aurora Subglacial Basin, East Antarctica, JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE, Vol: 117, ISSN: 2169-9003
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- Citations: 60
Siegert MJ, Clarke RJ, Mowlem M, et al., 2012, CLEAN ACCESS, MEASUREMENT, AND SAMPLING OF ELLSWORTH SUBGLACIAL LAKE: A METHOD FOR EXPLORING DEEP ANTARCTIC SUBGLACIAL LAKE ENVIRONMENTS, REVIEWS OF GEOPHYSICS, Vol: 50, ISSN: 8755-1209
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- Citations: 39
Siegert MJ, Woodward J, Royston-Bishop G, 2012, Antarctic subglacial lakes, Encyclopedia of Earth Sciences Series, Pages: 37-39
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- Citations: 1
Woodward J, Siegert MJ, Smith AM, et al., 2012, Antarctic subglacial lake ellsworth, Encyclopedia of Earth Sciences Series, Pages: 31-34
Royston-Bishop G, Siegert MJ, Woodward J, 2012, Antarctic subglacial lake vostok, Encyclopedia of Earth Sciences Series, Pages: 34-37
Siegert M, 2011, Is there life in Lake Ellsworth?, Planet Earth, Pages: 28-29, ISSN: 1479-2605
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