scholarly journals Subglacial water pressure and ice-speed variations at Johnsons Glacier, Livingston Island, Antarctic Peninsula

2019 ◽  
Vol 65 (252) ◽  
pp. 689-699
Author(s):  
SHIN SUGIYAMA ◽  
FRANCISCO J. NAVARRO ◽  
TAKANOBU SAWAGAKI ◽  
MASAHIRO MINOWA ◽  
TAKAHIRO SEGAWA ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
High Frequency ◽  
Large Scale ◽  
Water Pressure ◽  
Borehole Data ◽  
Glacier Surface ◽  
Overburden Pressure ◽  
Livingston Island ◽  
The Antarctic ◽  
Measurement Period

ABSTRACTTo study subglacial hydrological condition and its influence on the glacier dynamics, we drilled Johnsons Glacier on Livingston Island in the Antarctic Peninsula region. Subglacial water pressure was recorded in boreholes at two locations over 2 years, accompanied by high-frequency ice-speed measurements during two summer melt seasons. Water pressure showed two different regimes, namely high frequency and large amplitude variations during the melt season (January–April) and small fluctuations near the overburden pressure the rest of the year. Speed-up events were observed several times in each summer measurement period. Ice motion during these events substantially contributed to total glacier motion, for example, fast ice flow over 1 week accounted for ~70% of the total displacement over a 25-day long measurement period. We did not find a clear relationship between subglacial water pressure and ice speed. This was probably because subglacial hydraulic conditions were spatially inhomogeneous and thus our borehole data did not always represent a large-scale subglacial condition. Ice temperature measurements in the boreholes confirmed the existence of a cold ice layer near the glacier surface. Our data provide a basis to better understand the dynamic and hydrological conditions of relatively unstudied glaciers in the Antarctic Peninsula region.

High-Frequency Modulated Signals Recorded Off the Antarctic Peninsula Area: Are Killer Whales Emitting Them?

2017 ◽  
Vol 45 (2) ◽  
pp. 253-260
Author(s):  
M. V. Reyes Reyes ◽  
S. Baumann-Pickering ◽  
A. Simonis ◽  
M. L. Melcón ◽  
J. Trickey ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
High Frequency ◽  
Killer Whales ◽  
Modulated Signals ◽  
The Antarctic

Subglacial hydrology modulates basal sliding response to climate forcing of the Antarctic ice sheet

2021 ◽  
Author(s):  
Elise Kazmierczak ◽  
Sainan Sun ◽  
Frank Pattyn
Keyword(s):  
Water Pressure ◽  
Ice Sheet ◽  
Effective Pressure ◽  
Rcp Scenarios ◽  
Overburden Pressure ◽  
Antarctic Ice Sheet ◽  
Surface Mass ◽  
Wide Range ◽  
Basal Sliding ◽  
The Antarctic

<p>Sliding laws determine to a large extent the sensitivity of the Antarctic ice sheet on centennial time scales (Pattyn, 2017, Bulthuis et al, 2019, Sun et al, 2020). Especially the contrast between linear and plastic sliding laws makes the latter far more responsive to changes at the grounding line. However, most studies neglect subglacial processes linked to those sliding laws. Subglacial hydrology may also play a role in modulating the amplitude of the reaction of marine ice sheets to forcing. Subglacial processes influence the effective pressure at the base. For a hard bed system, the latter can be defined by the ice overburden pressure minus the subglacial water pressure determined by routing of subglacial meltwater through a thin film. For soft-bed systems, the effective pressure is determined from till properties and physics. Here we investigate a wide range of subglacial processes and hydrology used in ice sheet models and implemented them in one ice sheet model (f.ETISh).</p><p> </p><p>The subglacial hydrology models and till deformation models are coupled to different sliding and friction laws (linear, power law, Coulomb), leading to 24 different representations. The Antarctic ice sheet model was then forced by the ISMIP6 forcing in surface mass balance and ocean temperature until 2100 for different RCP scenarios (Seroussi et al., 2020). Furthermore, to sample the intrinsic sensitivity we performed the ABUMIP experiments (Sun et al., 2020) for the full set of subglacial characteristics.  Results demonstrate that the type of sliding law is the most determining factor in the sensitivity of the ice sheet, modulated by the subglacial hydrology.</p>

New trigonioid bivalves from the Early Jurassic to earliest Cretaceous of the Antarctic Peninsula region: systematics and austral paleobiogeography

1995 ◽  
Vol 69 (1) ◽  
pp. 66-84 ◽  
Author(s):  
Simon R. A. Kelly
Keyword(s):  
New Zealand ◽  
Antarctic Peninsula ◽  
Southern Africa ◽  
Late Jurassic ◽  
Early Jurassic ◽  
South Shetland Islands ◽  
Shetland Islands ◽  
Livingston Island ◽  
History Of ◽  
The Antarctic

New discoveries of trigonioid bivalves are documented from three areas in the Antartic Peninsula: the Fossil Bluff Group of Alexander Island, the Latady Formation of the Orville Coast, and the Byers Group of Livingston Island, South Shetland Islands. Eleven taxa are described, representing six genera or subgenera. The faunas are characterized by genera including Vaugonia (Vaugonia), the first Early Jurassic trigonioid recognized on the continent; Vaugonia (V.) and V. (Orthotrigonia?) in the Late Jurassic; and Iotrigonia (Iotrigonia), Myophorella (Scaphogonia), and Pterotrigonia (Pterotrigonia), which span the Jurassic–Cretaceous boundary, reaching the Berriasian stage. The following species are new: Pterotrigonia (P.) cramei n. sp., Pterotrigonia (P.) thomsoni n. sp., Vaugonia (V.) orvillensis n. sp., and V. (Orthotrigonia?) quiltyi n. sp. The faunas show affinities with those of New Zealand and southern Africa. Trigonioids characterize the shallower marine biofacies in the Jurassic of the Antarctic and reflect the principal shallowing events in the history of the region.

scholarly journals Direct Measurement of Basal Water Pressures: Progress and Problemss

1979 ◽  
Vol 23 (89) ◽  
pp. 309-319 ◽  
Author(s):  
Steven M. Hodge
Keyword(s):  
Large Scale ◽  
Water Pressure ◽  
Water System ◽  
Water Levels ◽  
Hot Water ◽  
Overburden Pressure ◽  
Well Control ◽  
System A ◽  
Pressure Water ◽  
Internal Change

AbstractIn 1975 and 1977, 24 bore holes were drilled to the bed of South Cascade Glacier, Washington, U.S.A., using both electrothermal and hot-water drills. Only two holes connected directly with the basal water system, a significant decrease from the four to five such connections in 13 holes drilled in 1973 and 1974 (Hodge, 1976). Most of the bed, possibly as much as 90%, appears to be hydraulically inactive and isolated from a few active subglacial conduits. Bore holes which penetrate these inactive areas initially should connect eventually with the active basal water system due to bed pressurization by the water standing in the bore hole, provided there is a sufficient supply of water available to form and maintain the connection passageway. These sealed-off areas probably consist of the sub-sole drift and permeability barriers found recently at the bed of Blue Glacier by Engelhardt and others (1978); an increase in the area of bed covered by these features probably caused the decrease in chance of bore-hole connection. This apparently was not due to any external cause but rather was the result of a real internal change in the subglacial hydraulic system which occurred between 1974 and 1975.If most of the area of a glacier bed is hydraulically isolated sub-sole drift, or something similar, such features may well control large-scale glacier sliding changes, since changes in the amount of water having access to the glacier bed will take considerable time to affect the interstitial water pressure in the more widespread sub-sole drift.Water pressures in the active part of the basal water system of South Cascade Glacier are generally in the range of 50–75% of the ice overburden pressure. Water levels in a connected bore hole are probably representative over an area of the bed 100 m or more in extent. A correlation of bore-hole water levels with changes in surface motion supports the idea that the sliding of a temperate glacier is controlled largely by the basal water pressure.

scholarly journals Variations in ice rafted detritus on beaches in the South Shetland Islands: a possible climate proxy

2004 ◽  
Vol 16 (3) ◽  
pp. 339-344 ◽  
Author(s):  
BRENDA L. HALL ◽  
ETHAN R. PERRY
Keyword(s):  
Antarctic Peninsula ◽  
Ocean Circulation ◽  
Late Holocene ◽  
Warming Trend ◽  
South Shetland Islands ◽  
The South ◽  
Shetland Islands ◽  
Livingston Island ◽  
The Antarctic ◽  
Glacial Advance

Raised beach ridges on Livingston Island of the South Shetland Islands display variations in both quantity and source of ice rafted detritus (IRD) received over time. Whereas the modern beach exhibits little IRD, all of which is of local origin, the next highest beach (∼250 14C yr BP) has large amounts, some of which comes from as far away as the Antarctic Peninsula. Significant quantities of IRD also were deposited ∼1750 14C yr BP. Both time periods coincide with generally cooler regional conditions and, at least in the case of the ∼250 yr old beach, local glacial advance. We suggest that the increases in ice rafting may reflect periods of greater glacial activity, altered ocean circulation, and/or greater iceberg preservation during the late Holocene. Limited IRD and lack of far-travelled erratics on the modern beach are both consistent with the ongoing warming trend in the Antarctic Peninsula region.

Cretaceous angiosperms from an allegedly Triassic flora at Williams Point, Livingston Island, South Shetland Islands

1989 ◽  
Vol 1 (3) ◽  
pp. 239-248 ◽  
Author(s):  
P.M. Rees ◽  
J.L. Smellie
Keyword(s):  
Antarctic Peninsula ◽  
Direct Evidence ◽  
South Shetland Islands ◽  
Fossil Flora ◽  
Volcanic Arc ◽  
Shetland Islands ◽  
Active Volcanism ◽  
Livingston Island ◽  
Radiometric Ages ◽  
The Antarctic

A terrestrial sequence on Livingston Island, South Shetland Islands, known as the Williams Point Beds contains a well-preserved, diverse fossil flora previously assigned a Triassic age. Because of their supposed age, volcanic provenance and evidence for active volcanism, the Williams Point Beds have occupied a unique position in Gondwana (pre-Jurassic) stratigraphy in the Antarctic Peninsula region. However, a large new collection of plant specimens obtained at Williams Point has yielded several species of angiosperm leaves, which are abundant and occur at all levels within the Williams Point Beds sequence. Thus, a Triassic age is no longer tenable. On the basis of the plants present and published radiometric ages for associated strata, the Williams Point Beds fossil flora is reassigned to the Cretaceous, and there is some evidence for a more restricted Albian–Cenomanian age. This revision of the age of the Williams Point Beds removes all direct evidence for an active Triassic volcanic arc in the Antarctic Peninsula region.

scholarly journals Multi-decadal glacier surface lowering in the Antarctic Peninsula

2012 ◽  
Vol 39 (19) ◽  
pp. n/a-n/a ◽  
Author(s):  
Matthias Kunz ◽  
Matt A. King ◽  
Jon P. Mills ◽  
Pauline E. Miller ◽  
Adrian J. Fox ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Glacier Surface ◽  
The Antarctic

scholarly journals Dielectric Behaviour of Firn and Ice from the Antarctic Peninsula, Antarctica

1985 ◽  
Vol 31 (109) ◽  
pp. 253-262 ◽  
Author(s):  
John M. Reynolds
Keyword(s):  
Antarctic Peninsula ◽  
Thermal Regime ◽  
High Frequency ◽  
Relaxation Times ◽  
Dielectric Behaviour ◽  
Dielectric Analysis ◽  
Conductivity Data ◽  
Frequency Range ◽  
The Antarctic

AbstractDielectric experiments have been undertaken at temperatures between −2° and −70° C in the frequency range 10Hz to 100 kHz on 14 firn and ice samples retrieved from the Antarctic Peninsula. This investigation shows that the dielectric behaviour of polar samples from the Antarctic Peninsula is very similar to that of polar firn and ice from Greenland and from elsewhere in Antarctica. In contrast, temperate samples from the Antarctic Peninsula have relaxation times up to ten times shorter for a given temperature between –20° and –70°C, and have higher values of high-frequency conductivity than those of polar samples. Consequently, the thermal regime (temperate or polar) can be distinguished by the dielectric behaviour of the samples.High-frequency conductivities of polycrystalline samples from the Antarctic Peninsula match the trends of published conductivity data for HF- and HCl-doped laboratory ice; higher conductivities are associated with coastal sites where greater concentrations of marine ions occur in snow.Annealing polar firn above −10°C results in elevated conductivities across all frequencies measured and shortened relaxation times. Thus, samples for dielectric analysis should not be warmed to above –10°C for risk of irreversibly altering their dielectric behaviour.

Temperature Change on the Antarctic Peninsula Linked to the Tropical Pacific*

2013 ◽  
Vol 26 (19) ◽  
pp. 7570-7585 ◽  
Author(s):  
Qinghua Ding ◽  
Eric J. Steig
Keyword(s):  
Sea Ice ◽  
Antarctic Peninsula ◽  
Large Scale ◽  
Wave Train ◽  
Warming Trend ◽  
Tropical Pacific ◽  
The West ◽  
Spring Warming ◽  
Western Side ◽  
The Antarctic

Abstract Significant summer warming over the eastern Antarctic Peninsula in the last 50 years has been attributed to a strengthening of the circumpolar westerlies, widely believed to be anthropogenic in origin. On the western side of the peninsula, significant warming has occurred mainly in austral winter and has been attributed to the reduction of sea ice. The authors show that austral fall is the only season in which spatially extensive warming has occurred on the Antarctic Peninsula. This is accompanied by a significant reduction of sea ice cover off the west coast. In winter and spring, warming is mainly observed on the west side of the peninsula. The most important large-scale forcing of the significant widespread warming trend in fall is the extratropical Rossby wave train associated with tropical Pacific sea surface temperature anomalies. Winter and spring warming on the western peninsula reflects the persistence of sea ice anomalies arising from the tropically forced atmospheric circulation changes in austral fall.

scholarly journals Rapid accelerations of Antarctic Peninsula outlet glaciers driven by surface melt

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Peter A. Tuckett ◽  
Jeremy C. Ely ◽  
Andrew J. Sole ◽  
Stephen J. Livingstone ◽  
Benjamin J. Davison ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Water Pressure ◽  
Regional Climate ◽  
Dynamic Regime ◽  
Climate Modelling ◽  
Velocity Data ◽  
Ice Flow ◽  
Ice Velocity ◽  
Atmospheric Warming ◽  
The Antarctic

Abstract Atmospheric warming is increasing surface melting across the Antarctic Peninsula, with unknown impacts upon glacier dynamics at the ice-bed interface. Using high-resolution satellite-derived ice velocity data, optical satellite imagery and regional climate modelling, we show that drainage of surface meltwater to the bed of outlet glaciers on the Antarctic Peninsula occurs and triggers rapid ice flow accelerations (up to 100% greater than the annual mean). This provides a mechanism for this sector of the Antarctic Ice Sheet to respond rapidly to atmospheric warming. We infer that delivery of water to the bed transiently increases basal water pressure, enhancing basal motion, but efficient evacuation subsequently reduces water pressure causing ice deceleration. Currently, melt events are sporadic, so efficient subglacial drainage cannot be maintained, resulting in multiple short-lived (<6 day) ice flow perturbations. Future increases in meltwater could induce a shift to a glacier dynamic regime characterised by seasonal-scale hydrologically-driven ice flow variations.

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