Subglacial Rivers Research Articles

Insight into the relationships between total suspended particles and mercury in meltwater in a typical glacierized basin in the inland Tibetan Plateau

Mercury (Hg) released by melting glaciers is likely to bind to suspended particles in meltwater runoff, posing potential risks to downstream ecosystems. The rapidly receding glaciers on the Tibetan Plateau promote the export of total suspended particles (TSP), increasing the uncertainty of Hg export released by glacier melting. To investigate the relationships between TSP and Hg, a multimedia sampling campaign was conducted in July 2020 in the Kuoqionggangri glacier region of the Lhasa River Valley No. 1 glacierized basin located in the inland Tibetan Plateau. Samples from glacier snow/ice, supraglacial rivers, subglacial rivers, proglacial lakes, and meltwater runoff were obtained, and the relationships between TSP and Hg and their transport in glacier meltwater runoff in the context of glacier retreat were explored. The average TSP concentration of different environmental samples ranged from 9.51 mg/L to 399. 27 mg/L, showing significant differences. The average total Hg (THg) concentrations ranged from 0.52 ng/L to 58.81 ng/L and decreased in the order of snow/ice >runoff> subglacial river > proglacial lake > supraglacial river. Both TSP mass concentration and number concentration have an impact on the diurnal variation in meltwater runoff Hg, and the influence of TSP number concentration is stronger than that of concentration. Sites with high TSP concentrations and quantities tended to have higher Hg concentrations, while TSP particle size had no significant effect on Hg concentration or spatial distribution. Our study further divided the glacier recharge basin into the glacier cover zone, the periglacial zone, and the downstream zone and discussed the potential impact of TSP on Hg transport in each zone. Our analysis highlights that the periglacial zone will expand and activate the resuspension process of river sediments in the warming future, which may increase the export of TSP and Hg downstream.

Antarctic basal environment shaped by high-pressure flow through a subglacial river system

Antarctic basal environment shaped by high-pressure flow through a subglacial river system

Evolution of ice sheets on early Mars with subglacial river systems

Geological observations have revealed that early Martian terrains were carved with by numerous networks of valleys, which provides evidence that prolonged water activity sculpted the ancient surface of Mars during the late Noachian and the early Hesperian ages. Although such geological records would in theory require a large volume of liquid water under a long-term stable “warm and wet” climate, several model studies have indicated a contrasting “cold and icy” climate in early Mars, such that the formation of large-scale ice sheets on highlands would provide a vast reservoir of meltwater. In this study, we developed a global ice sheet model, named ALICE (Accumulation and ablation of Large-scale ICE-sheets with dynamics and thermodynamics) to perform the first simulation of the evolution of ice sheets coupled with a paleo-Mars global climate model. We began our calculations of glacial formation from the initial state with the ocean water amount corresponding to a 500 m global equivalent layer (GEL) for “cool and wet” atmospheric conditions with a surface pressure of 2 bar, H2 mixing ratios of 0% and 3%, and obliquities of 20°, 40°, and 60°.Our results show that all the water of the ocean and lakes were transferred to ice sheets within ~105 Mars years, and extensive ice sheets (thousands of meters in thickness) were formed in the southern low to middle latitudes. When geothermal heat flux was suitably high and the atmosphere contained 3% of H2, continuous subglacial melting supplied enough water due to widespread temperate-based ice sheets, forming runoff systems in the southern highlands where most valley networks are observed. With an obliquity of 40°, meltwater carved early Martian terrains within a relatively brief geological timescale (~105 Mars years). We also revealed that CO2 only atmosphere (H2 mixing ratio of 0%) could not reproduce temperate-based ice sheets and subglacial erosions even with assumed higher geothermal heat fluxes. There is still a possibility that several valleys were produced by short-lived climatic warming events, such as volcanism and meteorite impacts, which could produce the vast amount of meltwater required to sculpt valley systems.

Possible impacts of a 1000 km long hypothetical subglacial river valley towards Petermann Glacier in northern Greenland

Abstract. Greenland basal topographic data show a segmented valley extending from Petermann Fjord into the centre of Greenland; however, the locations of radar scan lines, used to create the bedrock topography data, indicate that valley segmentation is due to data interpolation. Therefore, as a thought experiment, simulations where the valley is opened are used to investigate its effects on basal water movement and distribution. The simulations indicate that the opening of this valley can result in an uninterrupted water pathway from the interior to Petermann Fjord. Along its length, the path of the valley progresses gradually down an ice surface slope, causing a lowering of ice overburden pressure that could enable water flow along its path. The fact that the valley base appears to be relatively flat and follows a path near the interior ice divide that roughly intersects the east and west basal hydrological basins is presented as evidence that its present day form may have developed in conjunction with an overlying ice sheet. Experiments where basal melting is increased solely within the deep interior near the known large area of basal melting result in an increase in the flux of water northwards along the entire valley. The results are consistent with a long subglacial river; however, considerable uncertainty remains over aspects such as whether adequate water is available at the bed, whether water escapes from the valley or is refrozen, and over what form a hydrological conduit could take along the valley base.

Examination of the interplay between glacial processes and exhumation in the Saint Elias Mountains, Alaska

The combination of large, temperate glaciers and rapid crustal convergence in the Saint Elias Mountains (southeastern Alaska, USA, and Yukon Territory and British Colombia, Canada) provides an exceptional opportunity to study the interactions between the tectonic and surface processes that have shaped most active orogens on Earth during much of the Quaternary. This research first provides a review of thermochronometric data sets recording exhumation under two major glacier systems of the Saint Elias Mountains, the Bagley-Bering and the Seward-Malaspina systems. These data sets are integrated over the single glacier systems and used in conjunction with glaciological data to investigate the interactions of glacial erosion and tectonics. Despite their proximity, the glaciological processes and geological settings of these two glacial systems differ significantly. On the east side of the orogen, sediments eroded from bedrock underneath the Malaspina Glacier reflect regions of rapid erosion under the slowly moving Seward Ice Field. Because the Seward Ice Field overlies a localized zone of major faulting and rapid exhumation, the strained and fractured bedrock is primed for erosion. On the west side, the Bering Glacier is the primary outlet for the Bagley Ice Field, which covers half of the crest of the orogen; however, few if any of the sediments at its terminus originate from under the Bagley Ice Field. Sediment transport is likely hindered by subglacial freeze-on processes that reduce the sediment-carrying capacity of subglacial rivers, though glacial surges are likely exceptions that deposit sediment far beyond the active margin of the glacier. Our study concludes that the widely invoked concepts of glacial erosion should be used with caution, as oversimplification can fail to account for important site-specific differences in geologic and glacial conditions.

Drainage pathways beneath ice sheets and their implications for ice sheet form and flow: the example of the British Ice Sheet during the Last Glacial Maximum

AbstractThe drainage system beneath ice sheets is poorly understood, even though it is a major determinant of their basal boundary condition, with implications for their form, flow and stability, and particularly of the ice streams that are crucial dynamic components. Understanding can be enhanced by evidence from the beds of former ice sheets. Glaciological principles are applied to geological evidence in the Vale of York that demonstrate occupancy by a major ice stream of the British ice sheet, with deduced gravitational shear stresses in the range 4–24 kPa, compared with a typical glacier shear stress of about 80–100 kPa, and horizontal velocities in the terminal zone in the range of 400–950 ma1. It is shown that the ice stream was in an almost buoyant state, with effective pressures in the range 50–100 kPa for a range of ice pressures between 2000 and 5000 kPa. Similar deductions are made for other ice streams on the southern flank of the British ice sheet. The esker system in the area of the ice stream represents locations of subglacial drainage tunnels that are suggested to be the key drainage elements in ice sheets where excess surface water penetrates to the bed. A theory of channel‐groundwater coupling which self‐organises in response to the rate of water recharge and the transmissivity of the subglacial bed is applied to the sub‐ice stream esker system. When matched to local geological evidence, the theory predicts the distribution of basal water pressures, the rate of recharge of surface water to the glacier bed, local shear stresses, the areal pattern of sedimentary processes including bed deformation, and their seasonal fluctuations. Predictions of the annual recharge rate of 950 mm are consistent with the modern values of modern mean annual rainfall in the Ouse (Vale of York) catchment of 906mm. The calculated mean annual discharge of the four major subglacial rivers in 55 m3s−1, compared with a mean flow of the modern Ouse of 49 m3s−1. A transient analysis shows the response time of water pressures in the underlying aquifer to changes in surface recharge to be of the order 10–100 days, suggesting the possibility of instabilities at the ice‐bed interface. It is not possible, however, to determine whether the Vale of York ice stream was characterized by stable or instable (surging) flow. Copyright © 2010 John Wiley & Sons, Ltd.

Nitrate production beneath a High Arctic glacier, Svalbard

Natural environmental isotopes of nitrate and ammonium are used in conjunction with major ion chemistry and hydrological data to establish controls upon the biogeochemical cycling of nitrogen beneath a High Arctic polythermal glacier (Midtre Lovénbreen). Here, high nitrate concentrations in subglacial meltwaters suggest that the subglacial environment may be furnishing nitrate in excess of that released from the snowpack and glacier ice. Isotopic values of δ 18O NO 3 suggest the provenance of such excess nitrate to be microbial in origin and δ 15N NO 3 indicates the source nitrogen compounds to have high δ 15N values relative to supraglacial runoff. We address the nitrification of supraglacial ammonium, the mineralization of organic nitrogen and the oxidation of geologic ammonium as potential sources of this additional nitrate. Mass fluxes of N compounds in a subglacial river and their δ 15N ratios indicate that the nitrification of supraglacial ammonium delivered to the glacier bed can account for much, but not all, of the excess nitrate. The additional source most likely involves the mineralization of organic nitrogen, although δ 15N values in rock samples suggest that the dissolution of rock-derived ammonium cannot be discounted if large fractionation effects occur during dissolution. Our results therefore agree with previous catchment scale mass balance studies at the site, which report a major internal loss of NH 4 + from the snowpack following melt. However, at the catchment scale, the NH 4 + loss is greater than the excess of NO 3 − observed in runoff, indicating that microbial assimilation of ammonia into organic matter in a range of other habitats is also likely. The identification of NH 4 +assimilation and nitrification further highlights the non-conservative behaviour of nitrogen in glacial environments and testifies to the importance of microbially-mediated reactions in the biogeochemical cycling of nitrogen in an environment that has, until recently, been regarded as biologically inert.

Forty-seven new subglacial lakes in the 0–110° E sector of East Antarctica

AbstractDuring the summer field seasons of 1987–91, studies of central East Antarctica by airborne radio-echo sounding commenced. This scientific work continued in the 1990s in the Vostok Subglacial Lake area and along the traverse route from Mirny, and led to the discovery of 16 new subglacial water cavities in the areas of Domes Fuji and Argus and the Prince Charles Mountains. Twenty-nine subglacial water cavities were revealed in the area near Vostok, along with a feature we believe to be a subglacial river. Two subglacial lakes were discovered along the Mirny–Vostok traverse route. These are located 50 km north of Komsomolskaya station and under Pionerskaya station. We find high geothermal heat flux in the vicinity of the largest of the subglacial lakes, and suggest this may be due to their location over deep faults where additional mantle heat is available.

Predicting settlement at a damsite on a tunnel valley deposit in Alberta

During investigations for a damsite on the Sand River, Alberta, an 80 m thick silt deposit in a valley some 500 m across was encountered. The most distinctive feature of the deposit is the uniformity of the silt, with thicknesses of up to 50 m occurring as a single layer uninterrupted by seams of significantly different material. The silt unit is believed to be the result of very uniform, prolonged depositional conditions in a subglacial river. The silt consists largely of silica grains between 10 and 60 μm, and although it contains clay, in some aspects its behaviour is close to that of sand.Evidence suggests that the present valley is a tunnel valley formed by meltwaters flowing through the underside of a glacier. The implications for the engineering geology of the damsite investigated are discussed and some geotechnical properties of this unusual silt deposit are presented, particularly as they affect settlement prediction. Key words: tunnel valley, glacial silt, earth dam, settlement, airphoto interpretation.

Melt-Water Drainage Pattern of Composite Glaciers

AbstractMedial moraines and lineations on the surface of composite glaciers enable the detection of structural and hydrological features. A study of the composite glacier Breidamerkurjökull, south Iceland, indicates relationships between subglacial waterways, ice structure in the junction area, and development of the glacier terminus. First, rivers are situated in or near medial moraines because melt water percolates to the bed and moves from there with the subglacial rivers mainly in the direction of ice flow. Secondly, the contact between two feeder glaciers sometimes forms an angle at the glacier terminus. Then the meltwater river escaping from the contact, generally in a radial direction (away from the glacier front), during the retreat will be transferred to the front of the first receding glacier. The drainage of the contact zone then changes from a radial to a tangential direction, destroying the terminal moraines of the recession stages.Similar relations are found in relics of Pleistocene ice sheets, two examples of which are compared. The huge subglacial channel of the Münsterländer Kiessandzug-Esker below the ice sheet of the Saalian glaciation in the Münsterland, north-west Germany, was formed in the ice-flow direction. It therefore gives details of the morphology and of the great ice-dammed lake east of the Teutoburger Wald ridge. At the contact between the Norwegian and Baltic Sea glaciers, the terminus formed an angle during the maximum extent of the Weichselian glaciation in northern Jutland. During retreat, the Norwegian glacier receded first. The large melt-water river escaping from the contact between both glaciers had formed the huge Karup Sandur during the maximum, but now, during the recession, it changed to the front of the Norwegian ice, destroying the recession moraines there.

Melt-Water Drainage Pattern of Composite Glaciers

Abstract Medial moraines and lineations on the surface of composite glaciers enable the detection of structural and hydrological features. A study of the composite glacier Breidamerkurjökull, south Iceland, indicates relationships between subglacial waterways, ice structure in the junction area, and development of the glacier terminus. First, rivers are situated in or near medial moraines because melt water percolates to the bed and moves from there with the subglacial rivers mainly in the direction of ice flow. Secondly, the contact between two feeder glaciers sometimes forms an angle at the glacier terminus. Then the meltwater river escaping from the contact, generally in a radial direction (away from the glacier front), during the retreat will be transferred to the front of the first receding glacier. The drainage of the contact zone then changes from a radial to a tangential direction, destroying the terminal moraines of the recession stages. Similar relations are found in relics of Pleistocene ice sheets, two examples of which are compared. The huge subglacial channel of the Münsterländer Kiessandzug-Esker below the ice sheet of the Saalian glaciation in the Münsterland, north-west Germany, was formed in the ice-flow direction. It therefore gives details of the morphology and of the great ice-dammed lake east of the Teutoburger Wald ridge. At the contact between the Norwegian and Baltic Sea glaciers, the terminus formed an angle during the maximum extent of the Weichselian glaciation in northern Jutland. During retreat, the Norwegian glacier receded first. The large melt-water river escaping from the contact between both glaciers had formed the huge Karup Sandur during the maximum, but now, during the recession, it changed to the front of the Norwegian ice, destroying the recession moraines there.

Les marges glacées du Loven Est, Spitsberg : un milieu original lié aux écoulements sous-glaciaires

Abstract. — During the autumn 1980, a subglacial river was discovered, traced upstream and mapped under the "Loven Est" (Spitsbergen). In the absence of knowledge of the water's origin, it was possible, in spring 1981, to understand the role of the subglacial run-off in the formation of the ice sheet in front of the glacier. The detailed observation of this distinctive locale has made possible the understanding of its formation and évolution. Lastly, this article surveys the studies of other ice sheets and permanent flows known in Spitsbergen.

The Evishanoran Esker, Tyrone.

A valuable monograph on “The Glacial Geology of the North-West of Ireland” (Proc. R. Irish Acad., xxxvi, 1924, pp. 174–314, pls. 8 and 9) by Professor J. K. Charlesworth describes the complex glacial phenomena of Tyrone. He endorses the main conclusion of my paper on the Irish Bskers (Phil. Trans. Roy. Soc., 1920, vol. 210, pp. 115–51) that they are usually deposited along the margin of a glacier, and are not due to subglacial rivers. The two works further agree in their rejection of the long advocated theory that Irish glaciation was dominated by a huge dome of ice which accumulated as snow above the Central Plain and over-rode the surrounding mountains. That view, due to Hull (Physic. Geol. and Geogr. Ireland, 1878, p. 228), has in later years been advocated, amongst others, by Mr. T. Hallissy (Proc. R. Irish Acad., xxxi, part 7, 1914, p. 9), and also by him in association with the late Professor Cole (Handb. Reg. Geol, Ireland, 1924, p. 46; Cole, ibid., British Isles, 1916, p. 328). The lines of ice movement marked on my map (op. cit., 1920, p. 143) illustrating the distribution of the Irish eskers are fundamentally inconsistent with the traditional theory; I am therefore glad to find that theory emphatically rejected by Professor Charlesworth. He adduces convincing evidence that the ice was formed on the mountains and flowed from them on to the plains. In two minor questions Professor Charlesworth differs from the views of my paper. I remarked (op. cit., p. 133) that the eskers of Tyrone are “different in several respects” from those of the Central Plain. I did not state the differences as I mentioned the Tyrone eskers only in reference to the subglacial formation of eskers; and as they gave no support to that process, I briefly referred to them as having had the same marginal origin as the typical eskers of the Central Plain.

IV.—The Irish eskers

The term esker is Irish and its definition should be settled by reference to the eskers of Ireland. They are hills of sand and gravel, which are typically ridges, but are sometimes mounds or groups of mounds. Excluding various suggestions only of historic interest, there are three chief theories of the formation of ridge-eskers. According to the first theory, due mainly to Hummel (1874, p. 3), eskers are accumulations of gravel along sub-glacial rivers. According to the second theory, due largely to Holst (1876-7, p. 97), eskers are deposited along rivers flowing either over, or perhaps partially within, glaciers. According to the third theory, which was advocated almost simultaneously by Hershey (1897, p. 241), Baron de Geer (1897, pp. 377-386), and Baron von Toll (1899, p. 22), eskers are the deltaic deposits of glacial rivers, and their ridged form is due to their continuous deposition at successive positions by the slow recession of the river mouth during the retreat of the ice sheet. An esker so formed should show an annual banding due to the seasonal variations in the volume of the glacial river. This banded structure is well developed in the Swedish osar (åsar), for many of which this receding delta theory may be regarded as established. Prof. Sollas adopted Hummel’s theory for the Irish eskers. He described them (1896, p. 803) as the casts of systems of sub-glacial rivers. He justly objected to the supraglacial theory, since the eskers were clearly accumulated in their present positions ( ibid ., p. 819) and had not been redeposited at a lower level on the melting of the ice. His map of the esker system of Central Ireland, compiled from the maps of the Geological Survey, shows some eskers arranged in convergent series like a river and its tributaries; and it was this arrangement which suggested the fluviatile origin of the osar of Sweden. The Irish eskers have therefore been regarded as exactly equivalent to the Swedish osar.

IV.—The Surface Geology of the North of Europe, as Illustrated by the Åsar or sar of Scandinavia and Finland

Let us next turn to the postulated subglacial rivers. How can we conceive of tunnels of ice 100 miles long runninginone direction, 300 feet high, and only 20 or 30 paces wide? The difficulty about the provenance of the stones, again, is equally great or even greater, and more insurmountable in such a case than it would be in the case already cited.

The Glaciation of Yorkshire

The address, of which the following is a rather free rendering, was delivered at very short notice. In its present form it is designed rather with a view to directing the attention of geologists to some of the larger problems connected with the glacial phenomena of Yorkshire than as an attempt to offer a full or final solution of them. I have elsewhere* stated, somewhat at length, the grounds upon which I have been led to reject the theory of a great submergence of England and Wales during the glacial period, and to ascribe the phenomena, to the operation of great glaciers with their concomitants of sub-glacial rivers, extra-morainie lakes. &c., acting upon a land-surface standing at about, and certainly not below, its present level. I have also specified the course, general effects and approximate limits of the glaciers so far as I had been able, either by a study of the literature of the subject, or in the field, to determine them. I may, however, briefly recapitulate the points germane to the present enquiry. The gradual approach of the ice-age produced at first small valley-glaciers in our great hill clusters, e.g. the Highlands and Southern uplands of Scotland, the Lake District, North and South Wales, the mountainous parts of Ireland, and perhaps some few valleys of the Pennine Chain. With the accentuation of the cold these glaciers grew, coalesced, and extended out upon the low grounds or into the sea according to situation. Such as reached the sea detached ...