scholarly journals Massive, ancient sea-ice strata and preserved physical-structural characteristics in the Ward Hunt Ice Shelf

1991 ◽  
Vol 15 ◽  
pp. 125-131 ◽  
Author(s):  
Martin O. Jeffries
Keyword(s):  
Sea Ice ◽  
Structural Characteristics ◽  
Ice Core ◽  
Gravity Drainage ◽  
Physical Processes ◽  
Ice Shelf ◽  
The West ◽  
Time Intervals ◽  
Long Time ◽  
Equilibrium Thickness

Two sea-ice layers, one measured as 9 m thick, the other at least 12 m thick and estimated to be 24.5 m thick, have been located by ice core drilling in the west Ward Hunt Ice Shelf. To examine the preservation of physical-structural characteristics over long time intervals, the crystal structure and brine volumes in the sea ice, which possibly dates back to about 3000 BP, have been studied. The structural characteristics are immediately recognizable as those of undeformed congelation sea ice accreted by Stefan growth. Brine volumes in the ancient sea ice are higher than those in modern multi-year ice at the same temperature. The preservation of brine over a time span of hundreds to thousands of years is attributed to an absence of surface meltwater to effect brine flushing and the very slow, even negligible action of gravity drainage, brine pocket migration and brine expulsion. The congelation structures indicate that sea ice can grow by the Stefan accretion mechanism to thicknesses exceeding the equilibrium thickness (2.5–5 m) of most undeformed multi-year ice. The observed physical-structural characteristics of the Ward Hunt sea ice strongly suggest that many of the properties attained by sea ice are permanent and not affected by slow-acting physical processes.

scholarly journals Massive, ancient sea-ice strata and preserved physical-structural characteristics in the Ward Hunt Ice Shelf

1991 ◽  
Vol 15 ◽  
pp. 125-131 ◽  
Author(s):  
Martin O. Jeffries
Keyword(s):  
Sea Ice ◽  
Structural Characteristics ◽  
Ice Core ◽  
Gravity Drainage ◽  
Physical Processes ◽  
Ice Shelf ◽  
The West ◽  
Time Intervals ◽  
Long Time ◽  
Equilibrium Thickness

Two sea-ice layers, one measured as 9 m thick, the other at least 12 m thick and estimated to be 24.5 m thick, have been located by ice core drilling in the west Ward Hunt Ice Shelf. To examine the preservation of physical-structural characteristics over long time intervals, the crystal structure and brine volumes in the sea ice, which possibly dates back to about 3000 BP, have been studied. The structural characteristics are immediately recognizable as those of undeformed congelation sea ice accreted by Stefan growth. Brine volumes in the ancient sea ice are higher than those in modern multi-year ice at the same temperature. The preservation of brine over a time span of hundreds to thousands of years is attributed to an absence of surface meltwater to effect brine flushing and the very slow, even negligible action of gravity drainage, brine pocket migration and brine expulsion. The congelation structures indicate that sea ice can grow by the Stefan accretion mechanism to thicknesses exceeding the equilibrium thickness (2.5–5 m) of most undeformed multi-year ice. The observed physical-structural characteristics of the Ward Hunt sea ice strongly suggest that many of the properties attained by sea ice are permanent and not affected by slow-acting physical processes.

scholarly journals Water Circulation and Ice Accretion Beneath Ward Hunt Ice Shelf (Northern Ellesmere Island, Canada), Deduced From Salinity and Isotope Analysis of Ice Cores

1988 ◽  
Vol 10 ◽  
pp. 68-72 ◽  
Author(s):  
Martin O. Jeffries ◽  
William M. Sackinger ◽  
H. Roy Krouse ◽  
Harold V. Serson
Keyword(s):  
Sea Ice ◽  
Fresh Water ◽  
Sea Water ◽  
Ice Core ◽  
Isotope Analysis ◽  
Ice Cores ◽  
Water Circulation ◽  
Ice Shelf ◽  
The West ◽  
Water Ice

Ice-core drilling and ice-core analysis (electrical conductivity–salinity, 18O, 3H, density) reveal that the internal structure of the west Ward Hunt Ice Shelf contrasts sharply with that of the east ice shelf. The west ice shelf contains a great thickness (≥22 m) of sea ice (mean salinity, 2.22‰; mean δ18O, -0.8‰), whereas the east ice shelf is entirely of meteoric or fresh-water ice (mean salinity 0.01‰; mean δ18O, -29.7‰). High tritium activities are found only in ice from near the bottom of the east and west ice shelves. The contrasting ice-core data is considered to be a proxy record of variations in water circulation and bottom freezing beneath the ice shelf. The west shelf is underlain by sea water flowing into Disraeli Fiord. Sea ice accretes on to the bottom of the west ice shelf from the sea-water flowing into the fiord. Sea-water flowing out of the fiord is directed below the east ice shelf. However, the east ice shelf is not underlain directly by sea-water but by a layer of fresh water from the surface of Disraeli Fiord. In this region, ice growth resulting from the presence of this stable fresh-water layer has been accompanied by surface ablation over a period of perhaps the last 450 years. As a result, fresh-water ice has completely replaced any sea ice that originally grew in the region of the east ice shelf. Whereas the west and east shelves are underlain almost exclusively by sea-water and fresh water, ice in the south shelf is the result of freezing of fresh, brackish or sea water. This is attributed to mixing of the inflowing and outflowing waters.

scholarly journals Water Circulation and Ice Accretion Beneath Ward Hunt Ice Shelf (Northern Ellesmere Island, Canada), Deduced From Salinity and Isotope Analysis of Ice Cores

1988 ◽  
Vol 10 ◽  
pp. 68-72 ◽  
Author(s):  
Martin O. Jeffries ◽  
William M. Sackinger ◽  
H. Roy Krouse ◽  
Harold V. Serson
Keyword(s):  
Sea Ice ◽  
Fresh Water ◽  
Sea Water ◽  
Ice Core ◽  
Isotope Analysis ◽  
Ice Cores ◽  
Water Circulation ◽  
Ice Shelf ◽  
The West ◽  
Water Ice

Ice-core drilling and ice-core analysis (electrical conductivity–salinity, 18O, 3H, density) reveal that the internal structure of the west Ward Hunt Ice Shelf contrasts sharply with that of the east ice shelf. The west ice shelf contains a great thickness (≥22 m) of sea ice (mean salinity, 2.22‰; mean δ18O, -0.8‰), whereas the east ice shelf is entirely of meteoric or fresh-water ice (mean salinity 0.01‰; mean δ18O, -29.7‰). High tritium activities are found only in ice from near the bottom of the east and west ice shelves. The contrasting ice-core data is considered to be a proxy record of variations in water circulation and bottom freezing beneath the ice shelf. The west shelf is underlain by sea water flowing into Disraeli Fiord. Sea ice accretes on to the bottom of the west ice shelf from the sea-water flowing into the fiord. Sea-water flowing out of the fiord is directed below the east ice shelf. However, the east ice shelf is not underlain directly by sea-water but by a layer of fresh water from the surface of Disraeli Fiord. In this region, ice growth resulting from the presence of this stable fresh-water layer has been accompanied by surface ablation over a period of perhaps the last 450 years. As a result, fresh-water ice has completely replaced any sea ice that originally grew in the region of the east ice shelf. Whereas the west and east shelves are underlain almost exclusively by sea-water and fresh water, ice in the south shelf is the result of freezing of fresh, brackish or sea water. This is attributed to mixing of the inflowing and outflowing waters.

scholarly journals Impact of abrupt sea ice loss on Greenland water isotopes during the last glacial period

2019 ◽  
Vol 116 (10) ◽  
pp. 4099-4104 ◽  
Author(s):  
Louise C. Sime ◽  
Peter O. Hopcroft ◽  
Rachael H. Rhodes
Keyword(s):  
Sea Ice ◽  
Temperature Increase ◽  
General Circulation ◽  
Ice Core ◽  
Circulation Model ◽  
Ice Cores ◽  
Nitrogen Isotope ◽  
Ice Shelf ◽  
Last Glacial Period ◽  
Precipitation Seasonality

Greenland ice cores provide excellent evidence of past abrupt climate changes. However, there is no universally accepted theory of how and why these Dansgaard–Oeschger (DO) events occur. Several mechanisms have been proposed to explain DO events, including sea ice, ice shelf buildup, ice sheets, atmospheric circulation, and meltwater changes. DO event temperature reconstructions depend on the stable water isotope (δ18O) and nitrogen isotope measurements from Greenland ice cores: interpretation of these measurements holds the key to understanding the nature of DO events. Here, we demonstrate the primary importance of sea ice as a control on Greenland ice coreδ18O: 95% of the variability inδ18O in southern Greenland is explained by DO event sea ice changes. Our suite of DO events, simulated using a general circulation model, accurately captures the amplitude ofδ18O enrichment during the abrupt DO event onsets. Simulated geographical variability is broadly consistent with available ice core evidence. We find an hitherto unknown sensitivity of theδ18O paleothermometer to the magnitude of DO event temperature increase: the change inδ18O per Kelvin temperature increase reduces with DO event amplitude. We show that this effect is controlled by precipitation seasonality.

scholarly journals Stratigraphy, stable isotopes and salinity in multi-year sea ice from the rift area, south George VI Ice Shelf, Antarctic Peninsula

1991 ◽  
Vol 37 (127) ◽  
pp. 357-367
Author(s):  
J.-L. Tison ◽  
E. M. Morris ◽  
R. Souchez ◽  
J. Jouzel
Keyword(s):  
Stable Isotopes ◽  
Sea Ice ◽  
Fresh Water ◽  
Large Scale ◽  
Sea Water ◽  
Ice Core ◽  
Ice Shelf ◽  
The Core ◽  
Brackish Ice ◽  
Ice Production

AbstractResults from a detailed profile in a 5.54 m multi-year sea-ice core from the rift area in the southern part of George VI Ice Shelf are presented. Stratigraphy, stable isotopes and Na content are used to investigate the growth processes of the ice cover and to relate them to melting processes at the bottom of the ice shelf.The thickest multi-year sea ice in the sampling area appears to be second-year sea ice that has survived one melt season. Combined salinity/stable-isotope analyses show large-scale sympathetic fluctuations that can be related to the origin of the parent water. Winter accretion represents half of the core length and mainly consists of frazil ice of normal sea-water origin. However, five major dilution events of sea water, with fresh-water input from the melting base of the ice shelf reaching 20% on two occasions, punctuate this winter accretion. Two of them correspond to platelet-ice production, which is often related to the freezing of ascending supercooled water from the bottom of the ice shelf.Brackish ice occurs between 450 and 530 cm in the core. It is demonstrated that this results from the freezing of brackish water (Jeffries and others, 1989) formed by mixing of normal sea water with melted basal shelf ice, with dilution percentages of maximum 80% fresh water.

scholarly journals Stratigraphy, stable isotopes and salinity in multi-year sea ice from the rift area, south George VI Ice Shelf, Antarctic Peninsula

1991 ◽  
Vol 37 (127) ◽  
pp. 357-367 ◽  
Author(s):  
J.-L. Tison ◽  
E. M. Morris ◽  
R. Souchez ◽  
J. Jouzel
Keyword(s):  
Stable Isotopes ◽  
Sea Ice ◽  
Fresh Water ◽  
Large Scale ◽  
Sea Water ◽  
Ice Core ◽  
Ice Shelf ◽  
The Core ◽  
Brackish Ice ◽  
Ice Production

AbstractResults from a detailed profile in a 5.54 m multi-year sea-ice core from the rift area in the southern part of George VI Ice Shelf are presented. Stratigraphy, stable isotopes and Na content are used to investigate the growth processes of the ice cover and to relate them to melting processes at the bottom of the ice shelf.The thickest multi-year sea ice in the sampling area appears to be second-year sea ice that has survived one melt season. Combined salinity/stable-isotope analyses show large-scale sympathetic fluctuations that can be related to the origin of the parent water. Winter accretion represents half of the core length and mainly consists of frazil ice of normal sea-water origin. However, five major dilution events of sea water, with fresh-water input from the melting base of the ice shelf reaching 20% on two occasions, punctuate this winter accretion. Two of them correspond to platelet-ice production, which is often related to the freezing of ascending supercooled water from the bottom of the ice shelf.Brackish ice occurs between 450 and 530 cm in the core. It is demonstrated that this results from the freezing of brackish water (Jeffries and others, 1989) formed by mixing of normal sea water with melted basal shelf ice, with dilution percentages of maximum 80% fresh water.

scholarly journals Physical processes behind interactions of microplastic particles with natural ice

2022 ◽  
Author(s):  
Irina P Chubarenko
Keyword(s):  
Sea Ice ◽  
Ice Core ◽  
Ice Cores ◽  
Natural Environments ◽  
Polar Regions ◽  
Air Bubbles ◽  
Field Observations ◽  
Physical Processes ◽  
Ice Surface ◽  
Brittle Ductile Transition

Abstract Microplastic particles (MPs, <5 mm) are found in marine ice in larger quantities than in seawater, however, the distribution pattern within the ice cores is not consistent. To get insights into the most general physical processes behind interactions of ice and plastic particles in cool natural environments, information from academic and applied research is integrated and verified against available field observations. Non-polar molecules of common-market plastics are hydrophobic, so MPs are weak ice nucleators, are repelled from water and ice, and concentrate within air bubbles and brine channels. A large difference in thermal properties of ice and plastics favours concentration of MPs at the ice surface during freeze/thaw cycles. Under low environmental temperatures, falling in polar regions below the glass / brittle-ductile transition temperatures of the common-use plastics, they become brittle. This might partially explain the absence of floating macroplastics in polar waters. Freshwater freezes at the temperature well below that of its maximum density, so the water column is stably stratified, and MPs eventually concentrate at the ice surface and in air bubbles. In contrast, below growing sea ice, mechanisms of suspension freezing under conditions of (thermal plus haline) convection should permanently entangle MPs into ice. During further sea ice growth and aging, MPs are repelled from water and ice into air bubbles, brine channels, and to the upper/lower boundaries of the ice column. Sea ice permeability, especially while melting periods, can re-distribute sub-millimeter MPs through the brine channels, thus potentially introducing the variability of contamination with time. In accord with field observations, analysis reveals several competing factors that influence the distribution of MPs in sea ice. A thorough sampling of the upper ice surface, prevention of brine leakage while sampling and handling, considering the ice structure while segmenting the ice core – these steps may be advantageous for further understanding the pattern of plastic contamination in natural ice.

scholarly journals Basement Ige, Ward Hunt Ice Shelf, Ellesmere Island, Canada

1971 ◽  
Vol 10 (58) ◽  
pp. 93-100 ◽  
Author(s):  
J.B. Lyons ◽  
S.M. Savin ◽  
A.J. Tamburi
Keyword(s):  
Grain Boundary ◽  
Sea Ice ◽  
Small Angle ◽  
Brackish Water ◽  
Main Part ◽  
Ellesmere Island ◽  
Ice Shelf ◽  
The West ◽  
Vertical Orientation ◽  
Brackish Ice

Oxygen-isotope and chlorinity determinations, as well as petrographie observations, indicate that the basement we of the Ward Hunt Ice Shelf is largely composed of a unique brackish ice, which interdigitates with sea ice. Some iced firn occurs near the top of the Basement Ice, below an unconformity. stratification in brackish and sea ice represents annual increments to the bottom of the ice shelf The c-axis vertical orientation and small-angle grain-boundary relations in brackish ice are explained by nucleation and floating of ice dendrites from the undercooled brackish water zone to the bottom of the ice shelf, where they attach themselves sub-parallel to the plane of the undersurface. Ice island T-3 did not come from a break-up of the main part of the Ward Hunt Ice Shelf, but probably originated in a nearby area to the west.

scholarly journals Basement Ice, Ward Hunt Ice Shelf, Ellesmere Island, Canada

1971 ◽  
Vol 10 (58) ◽  
pp. 93-100 ◽  
Author(s):  
J.B. Lyons ◽  
S.M. Savin ◽  
A.J. Tamburi
Keyword(s):  
Grain Boundary ◽  
Sea Ice ◽  
Small Angle ◽  
Brackish Water ◽  
Main Part ◽  
Ellesmere Island ◽  
Ice Shelf ◽  
The West ◽  
Vertical Orientation ◽  
Brackish Ice

AbstractOxygen-isotope and chlorinity determinations, as well as petrographie observations, indicate that the basement we of the Ward Hunt Ice Shelf is largely composed of a unique brackish ice, which interdigitates with sea ice. Some iced firn occurs near the top of the Basement Ice, below an unconformity.stratification in brackish and sea ice represents annual increments to the bottom of the ice shelf The c-axis vertical orientation and small-angle grain-boundary relations in brackish ice are explained by nucleation and floating of ice dendrites from the undercooled brackish water zone to the bottom of the ice shelf, where they attach themselves sub-parallel to the plane of the undersurface.Ice island T-3 did not come from a break-up of the main part of the Ward Hunt Ice Shelf, but probably originated in a nearby area to the west.

WACSWAIN project: isotope and chemical ice core records from Skytrain Ice Rise, Antarctica

2021 ◽  
Author(s):  
Mackenzie Grieman ◽  
Helene Hoffmann ◽  
Jack Humby ◽  
Robert Mulvaney ◽  
Christoph Nehrbass-Ahles ◽  
...  
Keyword(s):  
Ice Core ◽  
Ice Sheet ◽  
Before Present ◽  
Last Interglacial ◽  
Ice Shelf ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Water Isotope

&lt;p&gt;The aim of the WArm Climate Stability of the West Antarctic ice sheet in the last INterglacial (WACSWAIN) project is to investigate the possible collapse of the West Antarctic Ice Sheet (WAIS) and its surrounding ice shelves during the Last Interglacial (~120,000 years ago).&amp;#160; As part of this project, a 651-meter ice core was drilled to bedrock at Skytrain Ice Rise in Antarctica during the 2018/2019 field season.&amp;#160; Ions and elements originating from marine sources along with water isotope content in this ice core can be used to infer changes in ice sheet and ice shelf extent.&amp;#160; The stable water isotope signal has the potential to capture both regional climate change and changes in the elevation of the drilling site through time.&amp;#160; Marine chemical content in the ice core could indicate variability in the proximity of the site to a marine environment.&amp;#160; Water isotopes and chemical impurities in the ice core were analysed continuously using cavity ring down spectroscopy and inductively coupled plasma mass spectrometry, respectively. As expected, &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O and &amp;#948;D increase from the last glacial maximum to the Holocene.&amp;#160; &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O and &amp;#948;D increase and sodium and magnesium levels decline from deglaciation into the early Holocene. &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O and &amp;#948;D show an abrupt increase in the early Holocene at about 8,000 years before present.&amp;#160; Sea salt similarly increases 2-fold and becomes more variable about 1,000 years later (7,000 years before present).&amp;#160; These increases could indicate a retreat of the ice shelf to its current position.&lt;/p&gt;

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