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 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 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 II. Ice observations

1859 ◽  
Vol 9 ◽  
pp. 609-611 ◽  
Keyword(s):  
Specific Gravity ◽  
Sea Ice ◽  
Fresh Water ◽  
Sea Water ◽  
Water Ice ◽  
Rate Of Growth ◽  
Abundant Evidence ◽  
Domestic Use ◽  
The Subject ◽  
Original Water

The contradictory statements of Dr. Sutherland and Dr. Kane, with regard to the saltness of the ice formed from sea-water,—the former maintaining that sea-water ice contains about one-fourth of the salt of the original water; the latter, that if the cold be sufficiently intense, there will be formed from sea-water a fresh and purer element fit for domestic use,—induced the author to take advantage of his position, as naturalist to the expedition now in the northern seas, to reinvestigate the subject. The changes which he has observed sea-water to undergo in freezing are the following. When the temperature falls below + 28°⋅5, it becomes covered with a thin pellicle of ice; after some time this pellicle becomes thicker and presents a vertically striated structure, similar to that of the ordinary cakes of sal-ammoniac. As the ice further increases in thickness, it becomes more compact, but the lowest portion still retains the striated structure. On the surface of the ice, saline crystals, designated by the author “efflorescence,” soon begin to form, at first few in number and widely separated, but gradually forming into tufts and ultimately covering the whole surface. At first, the increase in thickness of the ice is rapid, but afterwards the rate of growth is much slower and more uniform. The ice formed yields, on being melted, a solution differing in specific gravity according to the temperature at the time of congelation, its density being less, the lower the temperature at which the process of congelation took place. Although the author’s observations extended from + 28°⋅5 to —42°, he was never able to obtain fresh-water from sea-ice, the purest specimen being of specific gravity 1⋅005, and affording abundant evidence of the presence of salts, especially of chloride of sodium, in such quantity as to render it unfit for domestic purposes.

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.

New Light on the Mode of Uplift of the Fish and Fossiliferous Moraines of the Mcmurdo Ice Shelf, Antarctica

1965 ◽  
Vol 5 (42) ◽  
pp. 813-828 ◽  
Author(s):  
A. J. Gow ◽  
W. F. Weeks ◽  
G. Hendrickson ◽  
R. Rowland
Keyword(s):  
Fresh Water ◽  
Sea Water ◽  
Marine Invertebrate ◽  
Lower Surface ◽  
Faunal Remains ◽  
Ice Shelf ◽  
Water Ice ◽  
Deep Diving ◽  
Ice Surface ◽  
Fish Remains

Abstract The McMurdo Ice Shelf and associated faunal remains were examined in the vicinity of the easternmost Dailey Island. Stratigraphic, petrographic, and chemical composition studies of cores from two holes drilled through the ice shelf show that at these locations the shelf is composed only of fresh-water ice. Although cores from the deeper hole possessed typically glacial textures throughout, much of the ice from this part of the McMurdo Ice Shelf may have been formed from the freezing of a layer of fresh water found sandwiched between shelf bottom and the underlying sea-water. The existence of fresh water under the ice shelf can most probably be attributed to drainage of surface melt water during the ablation season. There was no evidence to indicate that this part of the McMurdo Ice Shelf is being nourished by the growth of sea ice onto its lower surface. The fish remains found on the ice surface were confined to a narrow zone along the tide crack and are believed to have been left in this vicinity by deep diving seals. The marine invertebrate remains on top of the ice are associated with morainal material and are believed to have been incorporated into the ice at the time of formation of the moraines.

scholarly journals Salinity and Isotope Analysis of Some Multi-Year Landfast Sea-Ice Cores, Northern Ellesmere Island, Canada

1988 ◽  
Vol 10 ◽  
pp. 63-67 ◽  
Author(s):  
Martin O. Jeffries ◽  
H. Roy Krouse
Keyword(s):  
Sea Ice ◽  
Sea Water ◽  
Growth Models ◽  
Isotope Analysis ◽  
Ice Cores ◽  
Double Diffusion ◽  
Ellesmere Island ◽  
Ice Growth ◽  
Water Stratification ◽  
Landfast Sea Ice

The salinity and isotope (18O, 3H) content of multi-year landfast sea-ice (MLSI) cores from northern Ellesmere Island, Canada, are examined. Salinity ranges from 0.01‰ to 4.54‰, and δ18O ranges from −23.8‰ to +0.7‰. Salinity and δ18O are linearly related, and tritium values generally exceed natural background levels. The results are evidence of ice growth associated with fresh-water / sea-water stratification below the ice. Salinity variations are cyclic and indicate a mean annual bottom accretion rate of 0.33–0.5 m a−1. Rather than signifying downward percolation of melt water from the surface, the ice δ values are a proxy measure of variations in salinity and 18O content of the water below the ice. Annual salinity layers are preserved in the absence of significant brine movement and ice deformation. The fast-ice environment appears to favour the maintenance of water stratification and growth of annual layers. It is suggested that ice growth in this environment is somewhat independent of thermodynamic sea-ice growth models; instead, ice growth by a double-diffusion process might account for the growth of MLSI beyond thicknesses normally encountered in undeformed multi-year pack-ice floes.

scholarly journals Salinity and Isotope Analysis of Some Multi-Year Landfast Sea-Ice Cores, Northern Ellesmere Island, Canada

1988 ◽  
Vol 10 ◽  
pp. 63-67 ◽  
Author(s):  
Martin O. Jeffries ◽  
H. Roy Krouse
Keyword(s):  
Sea Ice ◽  
Sea Water ◽  
Growth Models ◽  
Isotope Analysis ◽  
Ice Cores ◽  
Double Diffusion ◽  
Ellesmere Island ◽  
Ice Growth ◽  
Water Stratification ◽  
Landfast Sea Ice

The salinity and isotope (18O, 3H) content of multi-year landfast sea-ice (MLSI) cores from northern Ellesmere Island, Canada, are examined. Salinity ranges from 0.01‰ to 4.54‰, and δ18O ranges from −23.8‰ to +0.7‰. Salinity and δ18O are linearly related, and tritium values generally exceed natural background levels. The results are evidence of ice growth associated with fresh-water / sea-water stratification below the ice. Salinity variations are cyclic and indicate a mean annual bottom accretion rate of 0.33–0.5 m a−1. Rather than signifying downward percolation of melt water from the surface, the ice δ values are a proxy measure of variations in salinity and 18O content of the water below the ice. Annual salinity layers are preserved in the absence of significant brine movement and ice deformation. The fast-ice environment appears to favour the maintenance of water stratification and growth of annual layers. It is suggested that ice growth in this environment is somewhat independent of thermodynamic sea-ice growth models; instead, ice growth by a double-diffusion process might account for the growth of MLSI beyond thicknesses normally encountered in undeformed multi-year pack-ice floes.

New Light on the Mode of Uplift of the Fish and Fossiliferous Moraines of the Mcmurdo Ice Shelf, Antarctica

1965 ◽  
Vol 5 (42) ◽  
pp. 813-828 ◽  
Author(s):  
A. J. Gow ◽  
W. F. Weeks ◽  
G. Hendrickson ◽  
R. Rowland
Keyword(s):  
Fresh Water ◽  
Sea Water ◽  
Marine Invertebrate ◽  
Lower Surface ◽  
Faunal Remains ◽  
Ice Shelf ◽  
Water Ice ◽  
Deep Diving ◽  
Ice Surface ◽  
Fish Remains

AbstractThe McMurdo Ice Shelf and associated faunal remains were examined in the vicinity of the easternmost Dailey Island. Stratigraphic, petrographic, and chemical composition studies of cores from two holes drilled through the ice shelf show that at these locations the shelf is composed only of fresh-water ice. Although cores from the deeper hole possessed typically glacial textures throughout, much of the ice from this part of the McMurdo Ice Shelf may have been formed from the freezing of a layer of fresh water found sandwiched between shelf bottom and the underlying sea-water. The existence of fresh water under the ice shelf can most probably be attributed to drainage of surface melt water during the ablation season. There was no evidence to indicate that this part of the McMurdo Ice Shelf is being nourished by the growth of sea ice onto its lower surface. The fish remains found on the ice surface were confined to a narrow zone along the tide crack and are believed to have been left in this vicinity by deep diving seals. The marine invertebrate remains on top of the ice are associated with morainal material and are believed to have been incorporated into the ice at the time of formation of the moraines.

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