Ice cores and climatic change

1977 ◽  
Vol 280 (972) ◽  
pp. 143-168 ◽  
Keyword(s):  
Ice Sheets ◽  
Ice Cores ◽  
Ice Age ◽  
Isotopic Ratios ◽  
Temperature Profiles ◽  
Physical Processes ◽  
Similar Relation ◽  
Stable Isotopic ◽  
Last Ice Age ◽  
Glacial Periods

The paper deals primarily with the use of stable isotopic ratios to determine the former climate of ice sheets. Studies of temperature profiles throughout ice sheets have shown that for at least several thousand years, changes of isotopic δ ratios have been proportional to changes of surface temperatures; this relationship is discussed in terms of the physical processes involved. It is considered reasonable to use a similar relation for earlier periods in Antarctica, but in Greenland the relation may have varied with time. When determining past climates from the isotopic record, allowances have to be made for changes in the flow and thickness of ice sheets during major glacial periods. These factors are considered in relation to major ice cores from Vostok and Byrd stations in Antarctica and from Camp Century in Greenland. Vostok is the simplest case glaciologically, Camp Century the most complex. On purely glaciological grounds it appears that the ice age gave way to present-day climates some 10 000 ± 1000 a B.P., the coldest period being 20 000 + 3000 a B.P., when the climate in Antarctica was 6-8 °C colder than at present. Glaciological data suggest a duration of 50 000 to 100 000 years for the last ice age. Before this period, climates in Greenland and Antarctica appear to have been around 2-3 °C warmer than at present.

scholarly journals Atmospheric Lead in Antarctic Ice during the Last Climatic Cycle

1988 ◽  
Vol 10 ◽  
pp. 5-9 ◽  
Author(s):  
Claude F. Boutron ◽  
Clair C. Patterson ◽  
Claude Lorius ◽  
V.N. Petrov ◽  
N.I. Barkov
Keyword(s):  
Isotope Dilution Mass Spectrometry ◽  
Ice Cores ◽  
Ice Age ◽  
Crustal Rock ◽  
Last Interglacial ◽  
Toxic Heavy Metal ◽  
Mass Spectrometry Technique ◽  
Spectrometry Technique ◽  
Last Ice Age ◽  
The Antarctic

Concentrations of lead (Pb) have been measured by the ultra-clean isotope dilution mass spectrometry technique in various sections of the Antarctic Dome C and Vostok deep ice cores, whose ages range from 3.85 to 155 ka B.P., in order to assess the natural, pre-human, sources of this toxic heavy metal in the global troposphere. Pb concentrations were very low, as low as about 0.3 pg Pb/g during the Holocene and probably during the last interglacial and part of the last ice age. On the other hand, they were quite high, up to about 40 pg Pb/g, during the Last Glacial Maximum and at the end of the penultimate ice age. Wind-blown dust from crustal rock and soil appears to be the main natural source of Pb in the global troposphere. Pb contribution from volcanoes is significant during periods of low Pb only. Contribution from the oceans is insignificant.

Paleoecology and Late Quaternary Environments of the Colorado Rockies

2001 ◽  
Author(s):  
Scott A. Elias
Keyword(s):  
North America ◽  
Late Quaternary ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Rocky Mountain ◽  
Mountain Region ◽  
Ice Age ◽  
Rocky Mountain Region ◽  
Last Ice Age ◽  
Teton Range

Present-day environments cannot be completely understood without knowledge of their history since the last ice age. Paleoecological studies show that the modern ecosystems did not spring full-blown onto the Rocky Mountain region within the last few centuries. Rather, they are the product of a massive reshuffling of species that was brought about by the last ice age and indeed continues to this day. Chronologically, this chapter covers the late Quaternary Period: the last 25,000 years. During this interval, ice sheets advanced southward, covering Canada and much of the northern tier of states in the United States. Glaciers crept down from mountaintops to fill high valleys in the Rockies and Sierras. The late Quaternary interval is important because it bridges the gap between the ice-age world and modern environments and biota. It was a time of great change, in both physical environments and biological communities. The Wisconsin Glaciation is called the Pinedale Glaciation in the Rocky Mountain region (after terminal moraines near the town of Pinedale, Wyoming; see chapter 4). The Pinedale Glaciation began after the last (Sangamon) Interglaciation, perhaps 110,000 radiocarbon years before present (yr BP), and included at least two major ice advances and retreats. These glacial events took different forms in different regions. The Laurentide Ice Sheet covered much of northeastern and north-central North America, and the Cordilleran Ice Sheet covered much of northwestern North America. The two ice sheets covered more than 16 million km2 and contained one third of all the ice in the world’s glaciers during this period. The history of glaciation is not as well resolved for the Colorado Front Range region as it is for regions farther north. For instance, although a chronology of three separate ice advances has been established for the Teton Range during Pinedale times, in northern Colorado we know only that there were earlier and later Pinedale ice advances. We do not know when the earlier advance (or multiple advances) took place. However, based on geologic evidence (Madole and Shroba 1979), the early Pinedale glaciation was more extensive than the late Pinedale was.

scholarly journals 10Be Concentrations in Antarctic Ice

1988 ◽  
Vol 10 ◽  
pp. 200-200
Author(s):  
J. Beer ◽  
H. Oeschger ◽  
G. Bonani ◽  
M. Suter ◽  
W. Wölfli
Keyword(s):  
Production Rate ◽  
Atmospheric Circulation ◽  
Ice Cores ◽  
Ice Age ◽  
Solar Modulation ◽  
Short Term ◽  
Cosmogenic Isotope ◽  
Last Ice Age ◽  
Low Precipitation ◽  
Good Agreement

Measurements of the cosmogenic isotope 10Be (T½ = 1.5 Ma) on Greenland ice cores produced interesting results. Variations in the 10Be concentrations can be interpreted in terms of changes in the production rate and in atmospheric circulation and deposition. During the Holocene, good agreement between short-term variations in 10Be and 14C indicates that the production rate of both isotopes was changing, probably due to solar modulation.During the last ice age, periods with significantly higher 10Be concentrations are observed. The good anti-correlation between 10Be and δ18O suggests that these intervals correspond to periods of low precipitation rates.Work on Antarctic ice cores is in progress, but only relatively few 10Be data have been published yet. 10 Be results from Antarctic ice cores are presented and compared with data from Greenland.

scholarly journals On the Relationship Between 18O/16O Ratios of Precipitation and Climate

1988 ◽  
Vol 10 ◽  
pp. 217 ◽  
Author(s):  
U. Siegenthaler
Keyword(s):  
Water Vapour ◽  
Accumulation Rate ◽  
Ice Cores ◽  
Ice Age ◽  
Mean Annual Temperature ◽  
Mixing Ratio ◽  
Physical Processes ◽  
Monthly Data ◽  
Quantitative Understanding ◽  
The Relationship

A quantitative interpretation of oxygen-isotope data in ice cores in terms of climate has so far been hampered by the lack of a quantitative understanding of the processes which determine the isotopic composition of precipitation. Dansgaard (1964) has demonstrated that observed relations between 18O/16O and temperature can be explained reasonably well by the Rayleigh condensation model. This model is re-interpreted by noting that it predicts a dependence of the 18O/16O ratio on the water-vapour mixing ratio in the atmosphere. The relationship between the monthly data from different European stations and the water-vapour mixing ratio agrees remarkably well with the Rayleigh model. Data from Greenland snow show good correlation with the following parameters: mean annual temperature Ta, the water-vapour mixing ratio corresponding to Ta, and the accumulation rate. These correlations will be discussed in terms of the Rayleigh model and of the underlying physical processes. The correlation between 18O/16O ratios and the accumulation rate allows us to estimate the latter during the ice age. The change in the accumulation rate between the ice age and postglacial time can also be estimated from the chemical composition or the 10Be concentration. The different results will be compared.

scholarly journals A Detailed Analysis of the Rapid Changes in Ice-Core Parameters During the last Ice Age

1988 ◽  
Vol 10 ◽  
pp. 167-170 ◽  
Author(s):  
T. Staffelbach ◽  
B. Stauffer ◽  
H. Oeschger
Keyword(s):  
Molecular Diffusion ◽  
Ice Core ◽  
Ice Cores ◽  
Ice Age ◽  
Small Scale ◽  
Last Glaciation ◽  
Rapid Changes ◽  
Last Ice Age ◽  
Most Probable Explanation ◽  
Equal Density

Results from deep Greenland ice cores show rapid changes in several parameters in the deepest part. The most probable explanation for these variations is a fast-changing climate during part of the last glaciation. The question arises, however, of whether the observed changes in the ice cores could also be due to, or at least be influenced by, discontinuities in the stratigraphy. We present new CO2 and δ18O data from the Camp Century and Dye 3 deep ice cores. The data show rapid changes in CO2 and δ18O in both cores. One transition which was investigated in detail seems to be more rapid in the ice core from Dye 3 than in the Camp Century core. The broadening of a sharp δ18O transition due to molecular diffusion is discussed. Since this broadening is larger than the observed width of the transition, we discuss the possibility of a mechanism that can produce stratigraphic disturbances on a small scale. This mechanism is based on a calculation of the compression of horizontal layers which have equal density but different viscosities.

Climatic imprint in the mechanical properties of ice sheets and its effect on ice flow: Observations from South Pole and EPICA Dome C ice cores

2020 ◽  
Author(s):  
Carlos Martin ◽  
Howard Conway ◽  
Michelle Koutnik ◽  
Catherine Ritz ◽  
Thomas Bauska ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Crystal Orientation ◽  
Ice Core ◽  
Ice Sheets ◽  
Ice Cores ◽  
South Pole ◽  
Ice Flow ◽  
Phase Sensitive ◽  
Glacial Periods ◽  
Ice Core Records

<p>The climatic conditions over ice sheets at the time of snow deposition and compaction imprint distinctive crystallographic properties to the resulting ice. As the snow gets buried, its macroscopic structure evolves due to vertical compression but retains traces of the climatic imprint that generate distinctive mechanical, thermal and optical properties. Because climate alternates between glaciar periods, that are colder and dustier, and interglacial periods, the ice sheets are composed from layers with alternating mechanical properties. Here we compare ice core dust content and crystal orientation fabrics, from the ice core records, with englacial vertical strain-rates, measured with a phase-sensitive radar (ApRES), at South Pole and EPICA Dome C ice cores. Similarly to previous observations, we show that ice deposited during glacial periods develops stronger crystal orientation fabrics. In addition, we show that ice deposited during glacial periods is harder to vertically compress and horizontally extend, up to about 3 times, but softer to shear. These variations in mechanical properties are typically ignored in ice-flow modelling but they could be critical to interpret ice core records. Also, we show that the changes in crystal orientation fabrics due to transitions from interglacial to glacial conditions can be detected by phase-sensitive radar. This information can be used to constrain age-depth in future ice-core locations.</p>

Atmospheric Lead in Antarctic Ice during the Last Climatic Cycle

1988 ◽  
Vol 10 ◽  
pp. 5-9 ◽  
Author(s):  
Claude F. Boutron ◽  
Clair C. Patterson ◽  
Claude Lorius ◽  
V.N. Petrov ◽  
N.I. Barkov
Keyword(s):  
Isotope Dilution Mass Spectrometry ◽  
Ice Cores ◽  
Ice Age ◽  
Crustal Rock ◽  
Last Interglacial ◽  
Toxic Heavy Metal ◽  
Mass Spectrometry Technique ◽  
Spectrometry Technique ◽  
Last Ice Age ◽  
The Antarctic

Concentrations of lead (Pb) have been measured by the ultra-clean isotope dilution mass spectrometry technique in various sections of the Antarctic Dome C and Vostok deep ice cores, whose ages range from 3.85 to 155 ka B.P., in order to assess the natural, pre-human, sources of this toxic heavy metal in the global troposphere. Pb concentrations were very low, as low as about 0.3 pg Pb/g during the Holocene and probably during the last interglacial and part of the last ice age. On the other hand, they were quite high, up to about 40 pg Pb/g, during the Last Glacial Maximum and at the end of the penultimate ice age. Wind-blown dust from crustal rock and soil appears to be the main natural source of Pb in the global troposphere. Pb contribution from volcanoes is significant during periods of low Pb only. Contribution from the oceans is insignificant.

scholarly journals 10Be Concentrations in Antarctic Ice

1988 ◽  
Vol 10 ◽  
pp. 200
Author(s):  
J. Beer ◽  
H. Oeschger ◽  
G. Bonani ◽  
M. Suter ◽  
W. Wölfli
Keyword(s):  
Production Rate ◽  
Atmospheric Circulation ◽  
Ice Cores ◽  
Ice Age ◽  
Solar Modulation ◽  
Short Term ◽  
Cosmogenic Isotope ◽  
Last Ice Age ◽  
Low Precipitation ◽  
Good Agreement

Measurements of the cosmogenic isotope 10Be (T½ = 1.5 Ma) on Greenland ice cores produced interesting results. Variations in the 10Be concentrations can be interpreted in terms of changes in the production rate and in atmospheric circulation and deposition. During the Holocene, good agreement between short-term variations in 10Be and 14C indicates that the production rate of both isotopes was changing, probably due to solar modulation. During the last ice age, periods with significantly higher 10Be concentrations are observed. The good anti-correlation between 10Be and δ18O suggests that these intervals correspond to periods of low precipitation rates. Work on Antarctic ice cores is in progress, but only relatively few 10Be data have been published yet. 10 Be results from Antarctic ice cores are presented and compared with data from Greenland.

The invasion and colonization of the North Atlantic islands: a palaeoecological solution to a biogeographic problem

1986 ◽  
Vol 314 (1167) ◽  
pp. 619-635 ◽  
Keyword(s):  
North Atlantic ◽  
Endemic Species ◽  
Ice Age ◽  
The North ◽  
Northwest Europe ◽  
Ocean Surface Currents ◽  
Last Ice Age ◽  
The North Atlantic ◽  
Almost All ◽  
Glacial Periods

The North Atlantic islands, the Shetlands, Faeroes, Iceland and Greenland, have a flora and fauna with no truly endemic species. Their populations are dominated by Eurasian species, particularly conspicuous among which are the bulky flightless insects that should have found difficulty in reaching the islands after the retreat of the glaciers of the last ice age. The puzzling origin of this biota has been the subject of prolonged controversy. Most hypotheses have apparently insurmountable difficulties, largely because they are based on present-day observations augmented by presumed geological inferences for which there is very little hard supporting data. In recent years there has been a dramatic increase in our knowledge of the complexity of Quaternary events and also of the flora and fauna that lived along the southern margins of the ice sheets. It is suggested here that the islands lost almost all their biota at the height of the glacial periods and that they were invaded and colonized almost entirely from northwest Europe during the short phases at the end of the glacial periods, when fresh meltwater and ocean surface currents would have acted as potent aids to dispersal in the North Atlantic. It is suggested that the islands to the south of the major glacial influences, such as the Azores and Madeira, have endemic species because they were not subjected to the frequent exterminations and recolonizations that afflicted the islands further north. In testing this hypothesis, it has been possible to show that the carabid beetle faunas of the North Atlantic islands become more incomplete from east to west in terms of the potential numbers of species that each island could support, given its present-day climate and unimpeded access of invasion and colonization. This suggests a progressive loss of these earthbound insects as they were transported for increasing distances across a hostile ocean.

scholarly journals Glacial–interglacial shifts in global and regional precipitation δ<sup>18</sup>O

2015 ◽  
Vol 11 (2) ◽  
pp. 831-872 ◽  
Author(s):  
S. Jasechko ◽  
A. Lechler ◽  
F. S. R. Pausata ◽  
P. J. Fawcett ◽  
T. Gleeson ◽  
...  
Keyword(s):  
General Circulation ◽  
Late Holocene ◽  
Ice Cores ◽  
Ice Age ◽  
Proxy Record ◽  
Past Climate ◽  
Simulated Precipitation ◽  
Last Ice Age ◽  
The Tropics ◽  
Precipitation Δ18o

Abstract. Previous analyses of past climate changes have often been based on site-specific isotope records from speleothems, ice cores, sediments and groundwaters. However, in most studies these dispersed records have not been integrated and synthesized in a comprehensive manner to explore the spatial patterns of precipitation isotope changes from the last ice age to more recent times. Here we synthesize 88 globally-distributed groundwater, cave calcite, and ice core isotope records spanning the last ice age to the late-Holocene. Our data-driven review shows that reconstructed precipitation δ18O changes from the last ice age to the late-Holocene range from −7.1‰ (ice age δ18O < late-Holocene δ18O) to +1.8‰ (ice age δ18O > late-Holocene δ18O) with wide regional variability. The majority (75%) of reconstructions have lower ice age δ18O values than late-Holocene δ18O values. High-magnitude, negative glacial–interglacial precipitation δ18O shifts (ice age δ18O < late-Holocene δ18O by more than 3‰) are common at high latitudes, high altitudes and continental interiors. Conversely, lower-magnitude, positive glacial–interglacial precipitation δ18O shifts (ice age δ18O > late-Holocene δ18O by less than 2‰) are most common along subtropical coasts. Broad, global patterns of glacial–interglacial precipitation δ18O shifts are consistent with stronger-than-modern isotopic distillation of air masses during the last ice age, likely impacted by larger global temperature differences between the tropics and the poles. Further, to complement our synthesis of proxy-record precipitation δ18O, we compiled isotope enabled general circulation model simulations of recent and last glacial maximum climate states. Simulated precipitation δ18O from five general circulation models show better inter-model and model-observation agreement in the sign of δ18O changes from the last ice age to present day in temperate and polar regions than in the tropics. Further model precipitation δ18O research is needed to better understand impacts of inter-model spread in simulated precipitation fluxes and parameterizations of convective rainout, seawater δ18O and glacial topography on simulated precipitation δ18O. Future paleo-precipitation proxy record δ18O research can use new global maps of glacial δ18O reconstructions to target and prioritize regional investigations of past climate states.

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