Showing papers on "Antarctic sea ice published in 1980"
TL;DR: A considerable portion of Northern Eurasia, and particularly its continental shelf, was glaciated by inland ice during late Weichsel time as mentioned in this paper, which was first inferred from such evidence as glacial striae, submarine troughs, sea-bed diamictons, boulder trains on adjacent land, and patterns of glacioisostatic crustal movements.
332 citations
TL;DR: The authors showed that the occurrence of such a cold deep water mass implies that the North Atlantic was a sink for dense surface waters, replacing the Norwegian Sea where ice cover and stratification prevented the formation of deep water.
Abstract: Oxygen-18 records of benthic foraminifera from northeastern Atlantic and Southern Ocean cores are significantly different. This difference indicates that the deep water in the northeastern Atlantic Ocean during the last Ice Age was at least 1.3 °C cooler than in modern times. We show here that the occurrence of such a cold deep water mass implies that the North Atlantic was a sink for dense surface waters, replacing the Norwegian Sea where ice cover and stratification prevented the formation of deep water.
196 citations
TL;DR: The oxygen isotopic stage 5/4 boundary in deep-sea sediments marks a prominent interval of northern hemisphere ice-sheet growth that lasted about 10,000 yr.
147 citations
TL;DR: New techniques that have been used to obtain a continuous ice core through the whole 416-meter thickness of the Ross Ice Shelf at Camp J-9 have demonstrated that the bottom 6 meters of the ice shelf consists of sea ice.
Abstract: New techniques that have been used to obtain a continuous ice core through the whole 416-meter thickness of the Ross Ice Shelf at Camp J-9 have demonstrated that the bottom 6 meters of the ice shelf consists of sea ice. The rate of basal freezing that is forming this ice is estimated by different methods to be 2 centimeters of ice per year. The sea ice is composed of large vertical crystals, which form the waffle-like lower boundary of the shelf. A distinct alignment of the crystals throughout the sea ice layer suggests the presence of persistent long-term currents beneath the ice shelf.
120 citations
TL;DR: In this article, the volume of ground ice present in the upper 10 meters of Richards Island is calculated to be 10.27 km3, which constitutes over 80% of the total ice volume.
Abstract: Using data contained in the Mackenzie Valley Geotechnical Data Bank together with data derived from morphometric analyses of topographic maps and air photographs, the volume of ground ice present in the upper 10 m of Richards Island is calculated to be 10.27 km3. Pore and segregated ice constitute over 80% of the total ice volume. Wedge ice constitutes between 12 and 16% of total ice volume in the upper 4.5 m, and approximately 36% of all excess ice. In the upper 1–2 m, wedge ice may exceed 50% of earth materials. Pingo ice is insignificant in terms of its contribution to total ice volumes. Excess ice constitutes 14% of the upper 10 m of permafrost; it follows that thawing of this layer of permafrost may lead to an average subsidence of 1.4 m.The results of this study are probably typical of other areas of the Pleistocene Mackenzie delta. There is also general agreement with data obtained from arctic Alaska.
115 citations
TL;DR: In this paper, hydrographic, meteorological and ice floe data were collected over the Bering Sea shelf during March 1979, and the authors observed that a lens of less saline, colder water existed in the upper 20 m of the water column along the southern ice margin.
Abstract: During March 1979, hydrographic, meteorological and ice floe data were collected over the Bering Sea shelf. The ice pack extended to 59°however, there appeared to be little in situ freezing south of 62°N farther than 100 km from land. Hydrographic data from the southern margin of the ice (seaward limit) showed that a lens of less saline, colder water existed in the upper 20 m of the water column along the southern ice margin. During north-to-northeast wind events, floes were advected toward the south to southwest at rates as high as 0.5 m s−1 and rotted along the margin on the order of days. Little ridging of ice was observed over the open shelf. Rafting was prevalent among floes battered by wind and swell at the ice edge. Each year in the fall, northerly winds cool the water of Norton Sound and the Bering Sea north of St. Lawrence Island until the water column is isothermal and at freezing temperatures. Further cooling causes freezing. Under northerly wind conditions, ice is advected south into ...
111 citations
TL;DR: The sea ice microalgal communities and standing stock started to develop in late fall at the time of ice formation, grew very slowly through the winter months, exponentially increased in early spring, reached a peak just prior to the thaw period in late spring or early summer, and declined rapidly in summer as ice melting occurred.
Abstract: One hundred and ninety-six (196) species of microalgae were identified from the annual shore-fast sea ice samples collected from the Canadian Arctic between November and June in the years 1971 to 1978. The diatoms were represented by 189 species (21 centric and 168 pennate), the flagellates by three species, the dinoflagellates and chrysophytes by two species each. There were no blue-green algae. Species composition and distribution are tabulated. The dominant species of the microalgal communities in the bottom of the ice different from those found elsewhere in the ice. The sea ice microalgal communities and standing stock started to develop in late fall at the time of ice formation. They grew very slowly through the winter months, exponentially increased in early spring, reached a peak just prior to the thaw period in late spring or early summer, and declined rapidly in summer as ice melting occurred. Standing stock was greatest at the bottom of the sea ice, where it was one to two orders of magnitude larger than in other parts of the ice column, and 50 to 500 times greater than in the phytoplankton in the underlying waters. The ice communities consisted mainly of diatoms with a great majority of pennate forms. Large numbers of species and cells of diatoms were found at the bottom of the sea ice. Dinoflagellates, flagellates and chrysophytes occurred in relatively low numbers except in a few cases when ice blooms were observed. During May most of the sea ice microalgal blooms occurred in the bottom of the ice except for Phaeocystis pouchetii, which occurred elsewhere in the ice. Environmental factors controlling standing stock, growth and distribution of sea ice microalgae are discussed.
93 citations
TL;DR: The distribution of sea ice meltwater and meteoric water in the eastern Canadian Arctic has been studied by oxygen isotope techniques as discussed by the authors, showing that more than 25% of all the samples with sea ice input contained more sea ice than meteoric input.
Abstract: The distribution of sea ice meltwater and meteoric water in the eastern Canadian Arctic has been studied by oxygen isotope techniques The distribution pattern of sea ice meltwater is presented A comparison of the relative amounts of sea ice meltwater and meteoric water in the surface layer shows that more than 25% of all the samples with sea ice input contained more sea ice input than meteoric input Sea ice meltwater/meteoric water ratios as high as 47 have been observed The depth of sea ice meltwater penetration varies from 50 m in Baffin Bay to 140 m in Lancaster Sound Calculated sea ice thicknesses range from 05 to 45 m with a mean of 15 m, in good agreement with ice core data The significance of sea ice meltwater for chemical, physical, and biological oceanography is briefly discussed The principles and limitations of using oxygen isotopes to detect brines are discussed in the Baffin Bay setting The isotopic compositions of possible source waters for Baffin Bay bottom water are examined
87 citations
TL;DR: A review of the literature on shore ice pile-up and ride-up in arctic and subarctic waters is presented, along with an account of recent observations made by the authors as mentioned in this paper.
85 citations
TL;DR: In this paper, the expected increase of crystal size with age is observed in the ice deposited during the Holocene; further down major changes appear to be associated with climatic events and, in particular, with the transition from the last glacial age to present conditions.
81 citations
TL;DR: In this paper, an analysis of fluctuations in weekly mean percent ice cover, degree-days, and surface winds and monthly mean sea surface temperatures from the eastern Bering Sea shelf region is presented for the period 1973-1979.
Abstract: An analysis of fluctuations in weekly mean percent ice cover, degree-days, and surface winds and monthly mean sea surface temperatures from the eastern Bering Sea shelf region is presented for the period 1973–1979. The seasonal advance of the ice begins at the Bering Strait in November, reaches its southern maximum extent in March–April, and has completely disappeared by early July. Large year-to-year deviations from the seasonal means are observed in the data. These time series are divided into two sections with the first (∼1973–1976) characterized by lower (and slightly falling) temperatures and greater than normal (and slightly increasing) northerly surface winds and ice cover. The following period (∼1976–1979) is characterized by strong rises in air and sea temperatures, a precipitous fall in ice cover, and a fall in the northerly component of the surface wind with more southerly flow. These observations lead to a conceptual model in which the mean winter atmospheric circulation is the driving force behind the large year-to-year fluctuations in the various data sets. On shorter time scales, two relatively minor but persistent ice retreats are shown to occur each year generally around the end of December and the end of February. These retreats last 2–3 weeks, range between 5 and 20% reduction in ice cover and appear to be caused by south winds causing compaction of the ice edge. South winds associated with east sides of low-pressure systems, either progressing or retrograding over the Bering Sea, appear to be the driving force for this phenomenon.
01 Sep 1980
TL;DR: In this article, the monthly and seasonal means, extremes and variability of the Southern Hemisphere sea ice are examined for a five-year period and the variability is found to be greatest in the longitudes of the Antarctic coastal embayments, and a small but general decline in extent at all seasons throughout the period.
Abstract: The monthly and seasonal means, extremes and variability of the Southern Hemisphere sea ice are examined for a five year period. Its variability is found to be greatest in the longitudes of the Antarctic coastal embayments, and a small but general decline in extent at all seasons throughout the period is observed. At near maximum ice extent (July to November), the 5 year mean of the zonal westerlies to the north of the ice increases with increasing ice extent; however for individual years, at maximum ice extent, there is no clear correlation between zonally averaged ice extent and the strength of the zonal westerlies in the preceding or succeeding month. Comparison with the 5 year mean longitudinal pattern of atmospheric pressure maxima and minima at the latitude of the Antarctic trough points generally to asymmetries in the ice edge, such that it is further north and more variable in regions of frequent low pressure, and further south in regions of relatively high pressure. Examination of a specific longitudinal zone indicates that the pattern of ice extent is clearly regional, and apparently related to variations in the combined oceanic and atmospheric circulation particularly in the Antarctic embayments.
TL;DR: The Ross Ice Shelf is widely believed to be a Holocene feature, that is, during the late Pleistocene the inland (grounded) ice sheet extended out nearly to the continental shelf break in the Ross Sea, and retreated to its present position between 5,000 and 10,000 yr BP as discussed by the authors.
Abstract: The Ross Ice Shelf is widely believed to be a Holocene feature, that is, during the late Pleistocene the inland (grounded) ice sheet extended out nearly to the continental shelf break in the Ross Sea, and retreated to its present position between 5,000 and 10,000 yr BP. If so, and if the grounded ice sheet remained in that position for at least 10,000 yr, then a sea floor uplift of the order of 100 m is still to be expected in the grid western part of the Ross Ice Shelf. Even for a smaller and more ephemeral extension of the grounded ice, the uplift would still be several tens of metres. Recently reported measurements indicate that there are extensive areas near the present grounding line where the water layer beneath the ice shelf is thin enough so that uplift would lead to a grounding line advance of at least 100 km. As the sea floor depth generally increases towards the grid east, however, the maximum extent would not be past the middle of the present Ross Ice Shelf.
TL;DR: In this paper, an alternative and independent reconstruction method is given, where elevation and age data of sea levels from North America during the past 17,000 yr can be inverted to determine the history of the most recent North American ice sheet (Laurentide ice sheet), assuming the earth behaves as a viscoelastic material.
Abstract: Usually, ice sheets are reconstructed using the flow law of ice and a number of assumptions regarding ice sheet temperature, accumulation rate, and basal sliding resistance. In this paper, an alternative and independent reconstruction method is given. The weight of the ice sheets deformed the earth's surface and its geoid. The amount of deformation, which can be determined from presently emerged shorelines, is related to the thickness of the overlying ice burden. Therefore elevation and age data of sea levels from North America during the past 17,000 yr can be inverted to determine the history of the most recent North American ice sheet (Laurentide ice sheet), assuming the earth behaves as a viscoelastic material. Because of errors in the data and a number of simplifying assumptions, quadratic programing methods were necessary to insure that the predicted ice thicknesses of the past were always greater than at present. The predicted ice sheet is relatively thin (2000–3000 m), which suggests that it was very dynamic and probably not in a steady state. But poor resolution indicates that other ice thickness models, perhaps of greater thickness, may fit the sea level data as well. The fit to the data is, in general, good, and it indicates that a large proportion of the North American sea level data can be explained by glacial isostatic processes. However, at regions distant from the ice sheet (e.g., Florida) the fit is poor, because the assumption that water-loading effects can be ignored is no longer valid. For regions close to a fluctuating ice sheet margin (e.g., Connecticut) the fit to the data suffers because of the assumption that the areal extent of the ice sheet remained fixed through time. Methods are developed which obviate both of these unrealistic assumptions so that future inversion calculations will be more realistic. Furthermore, proglacial lake deleveling data can be used to extend the data set throughout the interior of North America so that the entire perimeter of the ice sheet is close to the constraining data. The error of fit and resolution may thus be improved considerably.
TL;DR: In this paper, the authors used Landsat satellite images of Ronne and Filchner ice shelves to identify surface features that indicate flow lines in the ice and their relationship to the major ice streams.
Abstract: Satellite images of Ronne and Filchner ice shelves show a variety of surface features many of which are believed to indicate flow lines in the ice. Sufficient imagery is now available from Landsat satellites to plot these features from mosaics. Although some of the features have been recognized from aircraft, it was not until an overall view was provided that the true extent of the features and their relationship to the major ice streams became apparent. Using this evidence together with published ice thickness data from radio echo and seismic sounding, flow patterns within the ice shelves and tributary glaciers can be inferred.
TL;DR: In this article, field observations in the Bering Sea show that because of the interaction of winds and ocean swell with the ice, the ice edge divides into three distinct zones: the edge, transition and interior.
Abstract: During March 1979 field observations in the Bering Sea show that because of the interaction of winds and ocean swell with the ice, the ice edge divides into three distinct zones. First, adjacent to the open ocean is an “edge" zone, 1–15 km in width, which consists of heavily rafted and ridged floes with thicknesses of 1–5 m and measuring 10–20 m on a side. Second is a “transition” zone measuring ∼5 km in width, which consists of rectangular ice floes with thicknesses of ∼0.5 m and measuring 20–40 m on a side. Third is the “interior” zone, which extends over hundreds of kilometers and consists of very large, relatively flat floes with thicknesses of ∼0.3 m. In the edge zone the incident swell causes the floes to fracture, raft and form pressure ridges, resulting in small thick floes. In the transition zone the swell amplitude is reduced to the point that the floes fracture in a rectangular pattern with very little rafting or ridging taking place. In the interior zone the swell amplitude is further...
TL;DR: In this paper, the authors present geomorphological evidence from Alexander Island and the Antarctic Peninsula which does not agree with either hypothesis, and show that following deglaciation from the Wisconsin maximum, there was less ice than at present around 8,000 yr ago.
Abstract: The West Antarctic ice sheet is believed to be inherently unstable because much of it is grounded below sea level1–4. It has been suggested that the ice sheet has withdrawn from its late Wisconsin maximum position, grounded at the edge of the continental shelf, and is now undergoing collapse as a delayed response to the warming and sea-level rise of the Holocene5, and that the ice sheet is likely to collapse shortly in response to rising CO2 levels in the atmosphere6. We present here some geomorphological evidence from Alexander Island and the Antarctic Peninsula which does not agree with either hypothesis. Rather, following deglaciation from the Wisconsin maximum, there was less ice than at present around 8,000 yr ago. The ice shelf in George VI Sound has built up subsequently.
TL;DR: In this paper, the differences between the two sets of mean atmospheric patterns were then found, and the student's t-test was used to establish the statistical significance, indicating that the wintertime (January-February) atmospheric circulation in the Pacific tends to be weaker during heavy ice conditions while the differences in the Atlantic are not as significant.
Abstract: Twenty-five years of Arctic sea ice data have been used in conjunction with data from the lower atmosphere (the surface and 700 mb) to establish some concurrent general circulation relationships. Five January climatologies for both maximum and minimum sea ice areas over the entire north polar cap were first determined. The differences between the two sets of mean atmospheric patterns were then found. The student's t-test was used to establish the statistical significance. The results indicate that the wintertime (January–February) atmospheric circulation in the Pacific tends to be weaker during heavy ice conditions while the differences in the Atlantic are not as significant. These results are compared with GCM (general circulation model) simulations with similar maximum ice conditions. Extremes in Arctic sea ice during January were also examined locally. Although extremes in sea ice between Greenland and northern Europe wore not found to be strongly associated with concurrent atmospheric changes...
TL;DR: In this paper, a cross-spectral analysis of the motion of four ice floes in the permanent arctic ice pack was performed during the summer of 1975 and the results showed that the local low-frequency surface motion is linearly related to local lowfrequency winds.
Abstract: Four ice floes in the permanent arctic ice pack were instrumented during the summer of 1975. Spectral and cross-spectral analysis of the complex time series of the ice motion and of the surface winds are given. The results show that the local low-frequency surface motion is linearly related to the local low-frequency winds. The higher frequency surface motion, including the significant inertial motion, cannot be entirely described by a linear model forced by the local winds. Cross-spectral analysis of the motion of floes separated by a hundred kilometers reveals a high coherency of the inertial motions. Two simple mathematical models are studied to explain observed cross spectra between stations. The spectral properties of these models are determined directly from the spectral properties of the winds. Qualitative agreement between the models and observations suggest that some coupling mechanism is at work in the ice pack even during summer.
TL;DR: New geophysical data from Taylor Glacier and the adjacent ice sheet in Victoria Land, Antarctica are presented in this paper, which challenge these suppositions and show that the East Anarctic ice sheet reached its maximum dimensions during each of the last four world-wide interglacials.
Abstract: Extent and volume of the Antarctic ice sheet have important roles in modulating global atmospheric and oceanographic processes and have significant implications for world sea levels1. The history of ice sheet variations in Antarctica has mainly been founded on studies in the ice free (Dry) valleys of southern Victoria Land (Fig. 1). A detailed glacial chronology by Denton and co-workers2–4 is based on the premise that Taylor Glacier and neighbouring Wright Upper Glacier are outlets of the East Antarctic ice sheet and that, “the extent of Taylor Glacier reflects the height of this ice sheet, and, since it terminates on land, records of its former positions provide one of the few indications of former heights of the ice sheet”5. That the East Anarctic ice sheet reached its maximum dimensions during each of the last four world-wide interglacials is an important conclusion of this work2. New geophysical data from Taylor Glacier and the adjacent ice sheet in Victoria Land, Antarctica are presented here which challenge these suppositions.
Journal Article•
TL;DR: In this paper, a triangulation survey of 20 stations in South Victoria Land has been conducted during the 1978-79 and 1979-80 field seasons to obtain the horizontal and vertical components of surface velocities of the ice sheet in the bare ice area at 18 stations and the parameters of surface strains at 18 triangles of the chain were obtained.
Abstract: National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, Houston, Texas 77058, U.S.A. Abstract: The mechanism of accumulation of a large number of meteorites in the bare ice area near the Allan Hills in South Victoria Land has been investi gated by surveying a triangulation chain of 20 stations, 15 km in total length, during the 1978-79 and 1979-80 field seasons. The horizontal and vertical components of surface velocities of the ice sheet in the bare ice area at 18 sta tions and the parameters of surface strains at 18 triangles of the chain were obtained. The horizontal velocity of the ice sheet at the station farthest from the datum point is 2.51 m/year and the velocity vector principally points in a northeast direction which is perpendicular to the contour lines. The magnitude of hori zontal velocities gradually decreases from a maximum at station 20 to nearly zero at the stations near the Allan Hills. The vertical movements of the bare ice are emergent at a rate of 4.5 cm/year on the average in the region of high me teorite accumulation, while in the area of the further inland the vertical ice flow shows small submergence velocities. Ablation rates are ranging from 4.2 to 7.0 cm/year with an average of 5.7 cm/year and are balanced on the average by the emergent velocity of the ice in the meteorite accumulation area. Compres sive strains are predominant in most of the triangle areas and the horizontal dilatation of each triangle area is negative (horizontal convergence). These characters of ice flow are favorable for accumulation of a large number of meteorites on the bare ice surface in a small area, and also support a pro posed hypothesis by NAGATA (1978) on the mechanism of concentration of Yamato meteorites within the Meteorite Ice Field near the Yamato Mountains in East Queen Maud Land, where the triangulation survey has also shown an upward flow of ice.
TL;DR: In this article, the authors calculate transient temperature profiles for an ice rise with a final summit thickness of 520 m that formed by grounding of ice shelf 420 m thick and estimate the age of a recently-formed ice rise by examining its temperature/depth profile.
Abstract: Ice rises form where an ice shelf runs aground on the sea bed. After grounding occurs, basal ice temperatures cool from the sea-water temperature towards an equilibrium temperature appropriate to grounded ice. This cooling can take many thousands of years, and much of the delay is due to the thermal inertia of the bedwck. Here, we calculate transient temperature profiles for an ice rise with a final summit thickness of 520 m that formed by grounding of ice shelf 420 m thick. Seventy-five per cent cooling of the basal ice takes between 7 000 and 11 500 years, depending on the " thermal memory" of the bedrock. This compares with an equivalent time of only 1 400 years if we neglect the thermal inertia of the bedrock. Because the surface slopes of the ice rise are related to the flow properties of the underlying ice, the summit thickness will tend to thicken as the basal ice cools. In principle, it should be possible to estimate the age of a recently-formed ice rise by examining its temperature/depth profile.
TL;DR: The use of active and passive microwave imagery in combination is the optimum way to observe the morphology and dynamics of near shore ice in the Beaufort Sea as mentioned in this paper, where the data from aircraft that are described in this paper are compared to the ESMR (Electrically Scanning Microwave Radiometer) imagery of the Nimbus-5 satellite.
Abstract: The use of active and passive microwave imagery in combination is the optimum way to observe the morphology and dynamics of near shore ice Active and passive microwave data from aircraft that are described in this paper are also compared to the ESMR (Electrically Scanning Microwave Radiometer) imagery of the Nimbus-5 satellite The information thus obtained shows how the data to be received from the SAR (Synthetic Aperture Radar) and SMMR (Scanning Multichannel Microwave Radiometer) and on Seasat A and Nimbus G have the potential of providing a vastly increased understanding of the near shore ice of the Beaufort Sea
01 Jan 1980
TL;DR: In this article, the authors summarize their knowledge on the sea ice conditions of the Greenland and Barents Seas and discuss the ice drift and the composition of the ice in these areas.
Abstract: The purpose of the present paper is to summarize our knowledge on the sea ice conditions of the Greenland and Barents Seas. The Atlantic sector of the Arctic may be divided into ... the East Greenland current, the Jan Mayen Gyre and the Barents Sea. The ice drift and the composition of the ice in these areas are discussed.
TL;DR: In this article, a number of experiments were carried out using side-scanning solar techniques for under-water mapping of icebergs, ice fronts, and ice walls, and for studies of active ploughing areas off ice fronts.
Abstract: During the Norwegian Antarctic Research Expedition of 1978–79, a number of experiments were carried out using side-scanning solar techniques for under-water mapping of icebergs, ice fronts, and ice walls, and for studies of active ploughing areas off ice fronts. This paper presents the techniques and some results, together with views on operational and environmental aspects of using side-scanning sonar in the Antarctic. From the sonographs it is possible to measure depths of icebergs and ice fronts, and to estimate the magnitudes of shape anomalies. Vertical profiles of ice fronts show great variations depending on whether they are grounded or floating. Also, the acoustic signatures vary according to the elapsed time since calving.
TL;DR: In this paper, the GLAS General Circulation Model (GCM) was applied to the four-month simulation of the thermodynamic part of the Parkinson-Washington sea ice model using atmospheric boundary conditions.
Abstract: The GLAS General Circulation Model (GCM) was applied to the four-month simulation of the thermodynamic part of the Parkinson-Washington sea ice model using atmospheric boundary conditions. The sea ice thickness and distribution were predicted for the Jan. 1-Apr. 30 period using the GCM-fields of solar and infrared radiation, specific humidity and air temperature at the surface, and snow accumulation; the sensible heat and evaporative surface fluxes were consistent with the ground temperatures produced by the ice model and the air temperatures determined by the atmospheric concept. It was concluded that the Parkinson-Washington sea ice model results in acceptable ice concentrations and thicknesses when used with GLAS GCM for the Jan.-Apr. period suggesting the feasibility of fully coupled ice-atmosphere simulations with these two approaches.