scholarly journals Surface-velocity field of the northern Larsen Ice Shelf, Antarctica

1994 ◽  
Vol 20 ◽  
pp. 319-326 ◽  
Author(s):  
R. A. Bindschadler ◽  
M. A. Fahnestock ◽  
P. Skvarca ◽  
T. A. Scambos
Keyword(s):  
Satellite Images ◽  
Surface Velocity ◽  
Ice Shelf ◽  
Limited Region ◽  
Surface Survey ◽  
Degree Of Confidence ◽  
High Degree ◽  
The Antarctic ◽  
Larsen Ice Shelf ◽  
Measurement Period

Three satellite images of the northern Larsen Ice Shelf arc used to derive velocity fields for the periods 1975–86 and 1986 89. Substantial increases in the speed of the ice between these periods are detected to a high degree of confidence. Ice which entered the ice shelf between Fothergill Point and Cape Worsley and ice from Drygalski Glacier has accelerated by approximately 15% over the measurement period. Ice from Bombardier and Dinsmoor Glaciers also exhibits acceleration but by a lesser amount. These accelerations may be the result of either significant retreat experienced by the ice shelf during this period or warming in the Antarctic Peninsula region. Velocities measured by surface survey over a 15 d period in 1991 indicate a slower velocity than the image-derived velocities in the limited region of overlap. These differences appear to be systematic and may be the result of uncontrolled errors in the surface survey. Limited control of one image could also contribute to some of these differences.

scholarly journals Surface-velocity field of the northern Larsen Ice Shelf, Antarctica

1994 ◽  
Vol 20 ◽  
pp. 319-326 ◽  
Author(s):  
R. A. Bindschadler ◽  
M. A. Fahnestock ◽  
P. Skvarca ◽  
T. A. Scambos
Keyword(s):  
Satellite Images ◽  
Surface Velocity ◽  
Ice Shelf ◽  
Limited Region ◽  
Surface Survey ◽  
Degree Of Confidence ◽  
High Degree ◽  
The Antarctic ◽  
Larsen Ice Shelf ◽  
Measurement Period

Three satellite images of the northern Larsen Ice Shelf arc used to derive velocity fields for the periods 1975–86 and 1986 89. Substantial increases in the speed of the ice between these periods are detected to a high degree of confidence. Ice which entered the ice shelf between Fothergill Point and Cape Worsley and ice from Drygalski Glacier has accelerated by approximately 15% over the measurement period. Ice from Bombardier and Dinsmoor Glaciers also exhibits acceleration but by a lesser amount. These accelerations may be the result of either significant retreat experienced by the ice shelf during this period or warming in the Antarctic Peninsula region. Velocities measured by surface survey over a 15 d period in 1991 indicate a slower velocity than the image-derived velocities in the limited region of overlap. These differences appear to be systematic and may be the result of uncontrolled errors in the surface survey. Limited control of one image could also contribute to some of these differences.

scholarly journals Changes in ice-shelf buttressing following the collapse of Larsen A Ice Shelf, Antarctica, and the resulting impact on tributaries

2016 ◽  
Vol 62 (235) ◽  
pp. 905-911 ◽  
Author(s):  
SAM ROYSTON ◽  
G. HILMAR GUDMUNDSSON
Keyword(s):  
Antarctic Peninsula ◽  
Surface Velocity ◽  
Ice Shelf ◽  
Mass Redistribution ◽  
Grounding Line ◽  
Modelling Studies ◽  
Speed Up ◽  
Stringent Test ◽  
The Antarctic ◽  
The Impact

ABSTRACTThe dominant mass-loss process on the Antarctic Peninsula has been ice-shelf collapse, including the Larsen A Ice Shelf in early 1995. Following this collapse, there was rapid speed up and thinning of its tributary glaciers. We model the impact of this ice-shelf collapse on upstream tributaries, and compare with observations using new datasets of surface velocity and ice thickness. Using a two-horizontal-dimension shallow shelf approximation model, we are able to replicate the observed large increase in surface velocity that occurred within Drygalski Glacier, Antarctic Peninsula. The model results show an instantaneous twofold increase in flux across the grounding line, caused solely from the reduction in backstress through ice shelf removal. This demonstrates the importance of ice-shelf buttressing for flow upstream of the grounding line and highlights the need to explicitly include lateral stresses when modelling real-world settings. We hypothesise that further increases in velocity and flux observed since the ice-shelf collapse result from transient mass redistribution effects. Reproducing these effects poses the next, more stringent test of glacier and ice-sheet modelling studies.

Jurassic trees at Jason Peninsula, Antarctica

1997 ◽  
Vol 9 (4) ◽  
pp. 443-444 ◽  
Author(s):  
R.A. del Valle ◽  
J.M. Lirio ◽  
J.C. Lusky ◽  
J.R. Morelli ◽  
H.J. Nuñez
Keyword(s):  
Antarctic Peninsula ◽  
Volcanic Rocks ◽  
Eastern Coast ◽  
Prominent Feature ◽  
Calc Alkaline ◽  
Ice Shelf ◽  
British Antarctic Survey ◽  
Antarctic Expedition ◽  
The Antarctic ◽  
Larsen Ice Shelf

Jason Peninsula (66°10'S, 61°00'W) is a prominent feature extending some 80 km into the Larsen Ice Shelf from the eastern coast of the Antarctic Peninsula, and consists of widely spaced rock exposures and several ice-domes with elevations up to some 600 m (Fig. 1). The feature was first seen from seaward on 1 December 1893 by Captain C.A. Larsen, who named one of the high summits “Mount Jason” after his ship. Leading the 1902–1904 Swedish Antarctic Expedition, Dr Otto Nordenskjöld observed the area from Borchgrevink Nunatak (66°03'S; 62°30'W) and reported that the summits seen by Larsen were separated from the Antarctic Peninsula. The name “Jason Island” was subsequently adopted for this feature, but in the 1950s researchers belonging to the currently named British Antarctic Survey (BAS) determined Larsen's discovery to be a large peninsula, underlain mainly by calc-alkaline volcanic rocks.

scholarly journals In-situ aircraft observations of ice concentrations within clouds over the Antarctic Peninsula and Larsen Ice Shelf

2012 ◽  
Vol 12 (7) ◽  
pp. 17295-17345
Author(s):  
D. P. Grosvenor ◽  
T. W. Choularton ◽  
T. Lachlan-Cope ◽  
M. W. Gallagher ◽  
J. Crosier ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Particle Production ◽  
Supercooled Liquid ◽  
Ice Crystals ◽  
Ice Crystal ◽  
Ice Shelf ◽  
Aircraft Observations ◽  
The Antarctic ◽  
Larsen Ice Shelf

Abstract. In-situ aircraft observations of ice crystal concentrations in Antarctic clouds are presented for the first time. Orographic, layer and wave clouds around the Antarctic Peninsula and Larsen Ice shelf regions were penetrated by the British Antarctic Survey's Twin Otter Aircraft, which was equipped with modern cloud physics probes. The clouds studied were mostly in the free troposphere and hence ice crystals blown from the surface are unlikely to have been a major source for the ice phase. The temperature range covered by the experiments was 0 to −21°C. The clouds were found to contain supercooled liquid water in most regions and at heterogeneous ice formation temperatures ice crystal concentrations (60 s averages) were often less than 0.07 l−1, although values up to 0.22 l−1 were observed. Estimates of observed aerosol concentrations were used as input into the DeMott et al., 2010 ice nuclei (IN) parameterisation. The observed ice crystal number concentrations were generally in broad agreement with the IN predictions, although on the whole the predicted values were higher. Possible reasons for this are discussed and include the lack of IN observations in this region with which to characterise the parameterisation, and/or problems in relating ice concentration measurements to IN concentrations. Other IN parameterisations significantly overestimated the number of ice particles. Generally ice particle concentrations were much lower than found in clouds in middle latitudes for a given temperature. Higher ice crystal concentrations were sometimes observed at temperatures warmer than −9 °C, with values of several per litre reached. These were attributable to secondary ice particle production by the Hallett Mossop process. Even in this temperature range it was observed that there were regions with little or no ice that were dominated by supercooled liquid water. It is likely that in some cases this was due to a lack of seeding ice crystals to act as rimers to initiate secondary ice particle production. This highlights the complicated nature of this process and indicates that the accurate representation of it in global models is likely to represent a challenge. However, the contrast between Hallett Mossop zone ice concentrations and the fairly low concentrations of heterogeneously nucleated ice suggests that the Hallet Mossop process has the potential to be very important in remote, pristine regions such as around the Antarctic coast.

scholarly journals In-situ aircraft observations of ice concentrations within clouds over the Antarctic Peninsula and Larsen Ice Shelf

2012 ◽  
Vol 12 (23) ◽  
pp. 11275-11294 ◽  
Author(s):  
D. P. Grosvenor ◽  
T. W. Choularton ◽  
T. Lachlan-Cope ◽  
M. W. Gallagher ◽  
J. Crosier ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Particle Production ◽  
Supercooled Liquid ◽  
Ice Crystals ◽  
Ice Crystal ◽  
Ice Shelf ◽  
Aircraft Observations ◽  
The Antarctic ◽  
Larsen Ice Shelf

Abstract. In-situ aircraft observations of ice crystal concentrations in Antarctic clouds are presented for the first time. Orographic, layer and wave clouds around the Antarctic Peninsula and Larsen Ice shelf regions were penetrated by the British Antarctic Survey's Twin Otter aircraft, which was equipped with modern cloud physics probes. The clouds studied were mostly in the free troposphere and hence ice crystals blown from the surface are unlikely to have been a major source for the ice phase. The temperature range covered by the experiments was 0 to −21 °C. The clouds were found to contain supercooled liquid water in most regions and at heterogeneous ice formation temperatures ice crystal concentrations (60 s averages) were often less than 0.07 l−1, although values up to 0.22 l−1 were observed. Estimates of observed aerosol concentrations were used as input into the DeMott et al. (2010) ice nuclei (IN) parameterisation. The observed ice crystal number concentrations were generally in broad agreement with the IN predictions, although on the whole the predicted values were higher. Possible reasons for this are discussed and include the lack of IN observations in this region with which to characterise the parameterisation, and/or problems in relating ice concentration measurements to IN concentrations. Other IN parameterisations significantly overestimated the number of ice particles. Generally ice particle concentrations were much lower than found in clouds in middle latitudes for a given temperature. Higher ice crystal concentrations were sometimes observed at temperatures warmer than −9 °C, with values of several per litre reached. These were attributable to secondary ice particle production by the Hallett Mossop process. Even in this temperature range it was observed that there were regions with little or no ice that were dominated by supercooled liquid water. It is likely that in some cases this was due to a lack of seeding ice crystals to act as rimers to initiate secondary ice particle production. This highlights the chaotic and spatially inhomogeneous nature of this process and indicates that the accurate representation of it in global models is likely to represent a challenge. However, the contrast between Hallett Mossop zone ice concentrations and the fairly low concentrations of heterogeneously nucleated ice suggests that the Hallet Mossop process has the potential to be very important in remote, pristine regions such as around the Antarctic coast.

scholarly journals Trace Elements in Simultaneously Sampled Aerosol and Snow from the Antarctic Peninsula (Abstract)

1988 ◽  
Vol 10 ◽  
pp. 201 ◽  
Author(s):  
Alan L. Dick
Keyword(s):  
Antarctic Peninsula ◽  
Sampling Period ◽  
Air Concentration ◽  
Ice Shelf ◽  
Surface Snow ◽  
Lead Zinc ◽  
The Antarctic ◽  
Fresh Surface ◽  
Larsen Ice Shelf ◽  
Snow Samples

Ultra-clean techniques have been used to collect a series of fresh surface-snow samples on Gipps Ice Rise, Larsen Ice Shelf (68°48′S, 60°54′W) between 21 December 1984 and 12 February 1985. Aerosol samples were collected simultaneously on to pre-cleaned membrane filters to allow the direct comparison of trace-element levels in air and snow. Samples have been analysed by various techniques for cadmium, copper, lead, zinc, aluminium, calcium, potassium and sodium. For all elements, cross-sample concentration profiles have been obtained to support the data for snow samples. The heavy-metal concentrations found in the surface snow were similar to those measured previously near Gomez Nunatak in the Antarctic Peninsula. The mean aerosol concentrations found at Gipps Ice Rise were Cd: 0.06 pg m−3, Cu: 1.0 pg m−3, Pb; 4.7 pg m−3, Zn: 6.1 pg m−3. These are the lowest concentrations measured so far in Antarctic aerosol. The ratio of the snow concentration (pg g−1) to air concentration (ng m−3), known as the washout factor, has been calculated for each element and sampling period. The data show that, for the Antarctic Peninsula, the marine aerosol is more efficiently removed to the snow-pack than is the crustal aerosol. Heavy metals are least efficiently removed. This result suggests that the measurement of concentrations in snow and ice alone may lead to misinterpretation of atmospheric source strengths.

Substantial changes in the coastline of Antarctica revealed by satellite imagery

Polar Record ◽  
1987 ◽  
Vol 23 (146) ◽  
pp. 577-583 ◽  
Author(s):  
J. G. Ferrigno ◽  
W. G. Gould
Keyword(s):  
Satellite Imagery ◽  
Shelf Area ◽  
Glacier Area ◽  
Ice Shelf ◽  
Glacier Tongue ◽  
Noaa Avhrr ◽  
The Antarctic ◽  
Larsen Ice Shelf

ABSTRACTNoaa Avhrr and Landsat MSS imagery acquired between January and November 1986 has shown substantial changes in the Antarctic coastline near the Filchner Ice Shelf, Larsen Ice Shelf and Thwaites Glacier. In the Filchner Ice Shelf area some 11,500 km of ice calved from mid-April onward. In the Larsen Ice Shelf area two large bergs calved between February and August. The combined volume of ice from these two events equals approximately three years' normal calving from the entire Antarctic coastline. In the Thwaites Glacier area several changes appear to have occurred at the base of Thwaites Iceberg Tongue and Thwaites Glacier Tongue.

scholarly journals Fast recession of the northern Larsen Ice Shelf monitored by space images

1993 ◽  
Vol 17 ◽  
pp. 317-321 ◽  
Author(s):  
Pedro Skvarca
Keyword(s):  
Remote Sensing ◽  
Antarctic Peninsula ◽  
Climatic Warming ◽  
Ice Shelf ◽  
Space Images ◽  
Front Position ◽  
Satellite Photograph ◽  
The Antarctic ◽  
Larsen Ice Shelf

The rapid retreat and disintegration of the Larsen Ice Shelf sector extending north of Seal Nunataks (65° S), documented from the mid 1970s onwards by remote sensing, is presented and related to the Antarctic Peninsula climatic warming recorded over several past decades. A 1975 KOSMOS satellite photograph and a series of LANDSAT MSS and TM images taken in 1978, 1979, 1986, 1988 and 1989 were used to monitor the retreat of the ice shelf between Seal Nunataks and Prince Gustav Channel. The ice shelf has decreased by more than 30% during the period 1975–89 within the Christensen Island to Cape Longing region. Measurements of the ice front position carried out in the field during late 1991 indicate that the recession between Lindenberg Island and Sobral Peninsula is still continuing, in some places at a rate of up to 2.5 km a−1.

scholarly journals Trace Elements in Simultaneously Sampled Aerosol and Snow from the Antarctic Peninsula (Abstract)

1988 ◽  
Vol 10 ◽  
pp. 201-201 ◽  
Author(s):  
Alan L. Dick
Keyword(s):  
Antarctic Peninsula ◽  
Sampling Period ◽  
Air Concentration ◽  
Ice Shelf ◽  
Surface Snow ◽  
Lead Zinc ◽  
The Antarctic ◽  
Fresh Surface ◽  
Larsen Ice Shelf ◽  
Snow Samples

Ultra-clean techniques have been used to collect a series of fresh surface-snow samples on Gipps Ice Rise, Larsen Ice Shelf (68°48′S, 60°54′W) between 21 December 1984 and 12 February 1985. Aerosol samples were collected simultaneously on to pre-cleaned membrane filters to allow the direct comparison of trace-element levels in air and snow. Samples have been analysed by various techniques for cadmium, copper, lead, zinc, aluminium, calcium, potassium and sodium. For all elements, cross-sample concentration profiles have been obtained to support the data for snow samples.The heavy-metal concentrations found in the surface snow were similar to those measured previously near Gomez Nunatak in the Antarctic Peninsula. The mean aerosol concentrations found at Gipps Ice Rise were Cd: 0.06 pg m−3, Cu: 1.0 pg m−3, Pb; 4.7 pg m−3, Zn: 6.1 pg m−3. These are the lowest concentrations measured so far in Antarctic aerosol.The ratio of the snow concentration (pg g−1) to air concentration (ng m−3), known as the washout factor, has been calculated for each element and sampling period. The data show that, for the Antarctic Peninsula, the marine aerosol is more efficiently removed to the snow-pack than is the crustal aerosol. Heavy metals are least efficiently removed. This result suggests that the measurement of concentrations in snow and ice alone may lead to misinterpretation of atmospheric source strengths.

Sign in / Sign up

Export Citation Format

Share Document