Comment on: Deglaciation of the Greenland and Laurentide ice sheets interrupted by glacier advance during abrupt coolings

AbstractThe pattern of horizontal strain rate in an ice sheet is discussed from a topological point of view. In a circularly symmetric ice sheet, the isotropic point for strain rate at its centre is degenerate and structurally unstable. On perturbation the degenerate point splits into two elementary isotropic points, each of which has the lemon pattern for the trajectories of principal strain rate. Contour maps of principal strain-rate values are presented which show the details of the splitting.

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Analysis and Simulation of Altimeter Performance for the Production of Ice Sheet Topographic Maps

Annals of Glaciology ◽

10.3189/s0260305500001324 ◽

1986 ◽

Vol 8 ◽

pp. 141-145 ◽

Cited By ~ 1

Author(s):

K.C. Partington ◽

C.G. Rapley

Keyword(s):

High Precision ◽

Systems Analysis ◽

Ice Sheets ◽

Ice Sheet ◽

Data Interpretation ◽

Topographic Maps ◽

Error Signal ◽

Tracking Systems ◽

Tracking Mode ◽

Non Linear

Satellite-borne, radar altimeters have already demonstrated an ability to produce high-precision, topographic maps of the ice sheets. Seasat operated in a tracking mode, designed for use over oceans, but successfully tracked much of the flatter regions of the ice sheet to ± 72° latitude. ERS-1 will extend coverage to ± 82° latitude and will be equipped with an ocean mode similar to that of Seasat and an ice mode designed to permit tracking of the steeper, peripheral regions. The ocean mode will be used over the flatter regions, because of its greater precision.Altimeter performance over the ice sheets has been investigated through a study of Seasat tracking behaviour and the use of an altimeter performance simulator, with a view to assessing the likely performance of ERS-1 and the design of improved tracking systems. Analysis of Seasat data shows that lock was frequently lost, as a result of possessing a non-linear height error signal over the width of the range window. Having lost lock, the tracker frequently failed to transfer rapidly and effectively to track mode. Use of the altimeter performance simulator confirms many of the findings from Seasat data and it is being used to facilitate data interpretation and mapping, through the modelling of waveform sequence.

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Mass Loss in the Greenland and Antarctica Ice Sheets: 2002-2014

SSRN Electronic Journal ◽

10.2139/ssrn.2684427 ◽

2015 ◽

Cited By ~ 2

Author(s):

Jamal Munshi

Keyword(s):

Mass Loss ◽

Ice Sheets

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ALPINE GLACIER ADVANCE DURING MIS 11 IN THE MCMURDO DRY VALLEYS, ANTARCTICA

10.1130/abs/2016ne-271625 ◽

2016 ◽

Author(s):

Kate M. Swanger ◽

◽

Joerg M. Schaefer ◽

Gisela Winckler

Keyword(s):

Mcmurdo Dry Valleys ◽

Dry Valleys ◽

Alpine Glacier ◽

Glacier Advance

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Antarctic Climate History and Global Climate Changes

10.1093/oxfordhb/9780190699420.013.18 ◽

2017 ◽

Author(s):

Pontus Lurcock ◽

Fabio Florindo

Keyword(s):

Ocean Circulation ◽

Climate Changes ◽

Numerical Models ◽

Global Climate ◽

Sediment Cores ◽

Ice Sheets ◽

Global Ocean ◽

Climate History ◽

Global Climate Changes ◽

Planetary Albedo

Antarctic climate changes have been reconstructed from ice and sediment cores and numerical models (which also predict future changes). Major ice sheets first appeared 34 million years ago (Ma) and fluctuated throughout the Oligocene, with an overall cooling trend. Ice volume more than doubled at the Oligocene-Miocene boundary. Fluctuating Miocene temperatures peaked at 17–14 Ma, followed by dramatic cooling. Cooling continued through the Pliocene and Pleistocene, with another major glacial expansion at 3–2 Ma. Several interacting drivers control Antarctic climate. On timescales of 10,000–100,000 years, insolation varies with orbital cycles, causing periodic climate variations. Opening of Southern Ocean gateways produced a circumpolar current that thermally isolated Antarctica. Declining atmospheric CO2 triggered Cenozoic glaciation. Antarctic glaciations affect global climate by lowering sea level, intensifying atmospheric circulation, and increasing planetary albedo. Ice sheets interact with ocean water, forming water masses that play a key role in global ocean circulation.

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A Lacustrine Glacier Retreat Sequence from the Permo-Carboniferous Dwyka Formation, Republic of South Africa

Journal of Glaciology ◽

10.1017/s0022143000030446 ◽

1983 ◽

Vol 29 (103) ◽

pp. 515-520

Author(s):

J. N. J. Visser

Keyword(s):

South Africa ◽

Lacustrine Sediments ◽

Glacier Retreat ◽

Marine Transgression ◽

Northern Margin ◽

Valley Fill ◽

Karoo Basin ◽

Ice Retreat ◽

Glacier Advance

Abstract The upper part of a Permo-Carboniferous glacial valley fill along the northern margin of the Karoo Basin includes glacio-lacustrine sediments. During the last glacier advance into the lake, a bedded heterogeneous diamictite facies was deposited and, on glacier retreat, a sequence of deformed siltstones with diamictite lenses and sandstone beds, varved shale and rhythmite shale was laid down. Black carbonaceous mud was deposited during the subsequent marine transgression. According to varve counts, the glacier receded from the valley over a period of 500 to 1 000 years and it is concluded that the overall ice-retreat rate during the Permo-Carboniferous deglaciation was relatively high.

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