Atmospheric Circulation during the Last Ice Age

1970 ◽  
Vol 1 (1) ◽  
pp. 29-58 ◽  
Author(s):  
H. H. Lamb ◽  
A. Woodroffe
Keyword(s):  
Flow Pattern ◽  
Atmospheric Circulation ◽  
Northern Hemisphere ◽  
Surface Pressure ◽  
Ice Age ◽  
Maximum Extent ◽  
General Flow ◽  
Marine Biological ◽  
Cold Stage ◽  
Last Ice Age

The prevailing surface temperatures in summer and winter at several different stages of the last ice age, indicated at various points scattered over the Northern Hemisphere, by botanical, glaciological, marine biological, oceanographic, etc. evidence, are used to derive probable distributions of 1000−500 mbar thickness, roughly equivalent to mean temperature of the lowest 5 km of the atmosphere and indicating the general flow pattern of the atmosphere in depth. From these thermal wind patterns computation of the tendency to cyclonic and anticyclonic development is possible. Maps of this development field, taken together with the indicated steering of surface cyclones and anticyclones by the thermal winds, make it possible to sketch probable distributions of surface pressure (and, by implication, surface winds) prevailing during each of the glacial stages studied. New light is thrown on the onset of glaciation and on the regimes associated with the maximum extent of glaciation, with the Alleröd warm epoch and the Post-Alleröd cold stage when there was some readvance of the ice.

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.

Atmospheric Circulation Patterns During Glacial Inception: A Possible Candidate

1984 ◽  
Vol 21 (1) ◽  
pp. 105-110 ◽  
Author(s):  
Thomas J. Crowley
Keyword(s):  
Snow Cover ◽  
Atmospheric Circulation ◽  
Northern Hemisphere ◽  
Circulation Pattern ◽  
Circulation Type ◽  
Ice Age ◽  
Similar Response ◽  
Present Climate ◽  
Atlantic Sector ◽  
Atmospheric Circulation Patterns

Models of atmospheric circulation in the North Atlantic sector during glacial inception can be expanded to a hemispheric scale with the aid of diagnostic studies of the present climate. The present “Greenland Above” (GA) atmospheric circulation type may be a candidate for the atmospheric circulation type required during glacial inception. The pattern is an amplification, with only minor phase shifts, of the present average winter circulation pattern in the extratropical Northern Hemisphere. Southerly flow in the northwest Atlantic is associated with warm ocean temperatures, low sea ice in the Davis Strait, and increased precipitation over northeast Canada. Evidence from modeling of the present climate indicates that the GA pattern could be maintained by increased snow cover over eastern North America. Enhanced snow cover, due to decreased Northern Hemisphere summer insolation, could cause a similar response on an ice-age time scale.

Volcanic dust in the atmosphere; with a chronology and assessment of its meteorological significance

1970 ◽  
Vol 266 (1178) ◽  
pp. 425-533 ◽  
Keyword(s):  
Atmospheric Circulation ◽  
Volcanic Eruptions ◽  
Ice Age ◽  
Polar Regions ◽  
Particle Sizes ◽  
Direct Effects ◽  
Northwest Europe ◽  
Circulation Parameters ◽  
Last Ice Age ◽  
Main Influence

After defining the terms commonly used in reporting volcanic eruptions and noting previous approaches to assessment of their magnitudes, this study proceeds to examine aspects of importance, or possible importance, to meteorology―principally the dust veils created in the atmosphere, particle sizes and distribution, heights, fall speeds and atmospheric residence times. Later sections deal with spread of the dust by the atmospheric circulation and the direct effects apparent upon radiation, surface temperature and extent of ice in the polar regions. These effects, as well as various crude measures of the total quantity of solid matter thrown up, are used to arrive at numerical assessments of volcanic eruptions in terms of a dust veil index (d. v. i.). The latitude of origin of the dust (latitude of the volcano) receives some attention, and apparently affects the course of development of the atmospheric circulation over the three or four years following, at least in the case of great eruptions (d. v. i. > 100 over one hemisphere). Effects upon the extent of ice on the polar seas may be of somewhat longer duration, and thereby influence the atmospheric circulation over a longer period of years, since there seems to be some association with the cumulative d.v.i. values when successive great eruptions occur with only few years between. The time distribution of volcanic dust since the last Ice Age, and since a. d. 1500, are indicated in as much detail as the evidence permits. Some associations with changes of climate are suggested, but it is clear that volcanic dust is not the only, and probably not the main, influence in this. The appendices give a chronology of eruptions (including those which it seems possible to dismiss as regards any effect on world weather or climate) and a chronology of d. v. i. values. A third appendix displays by means of graphs the variation of some circulation parameters in January and July in the region of northwest Europe over the years immediately following forty of the greatest eruptions since 1680.

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.

Seasonal variability in Northern Hemisphere atmospheric circulation during the Medieval Climate Anomaly and the Little Ice Age

2017 ◽  
Vol 165 ◽  
pp. 102-110 ◽  
Author(s):  
Thomas W.D. Edwards ◽  
Dan Hammarlund ◽  
Brandi W. Newton ◽  
Jesper Sjolte ◽  
Hans Linderson ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
Northern Hemisphere ◽  
Seasonal Variability ◽  
Little Ice Age ◽  
Ice Age ◽  
Medieval Climate Anomaly ◽  
Climate Anomaly

scholarly journals Zur letzten Eiszeit im alpinen und nordeuropäischen Raum

1987 ◽  
Vol 42 (2) ◽  
pp. 93-98 ◽  
Author(s):  
G. Glückert
Keyword(s):  
Fennoscandian Shield ◽  
Ice Age ◽  
Maximum Extent ◽  
Ice Caps ◽  
Last Glaciation ◽  
The Alps ◽  
Last Ice Age ◽  
Marginal Zones

Abstract. On the last Glaciation of the Alps and Fennoscandia. During the Pleistocene the Alps and the Fennoscandian Shield were covered several times with extensive ice caps. During the last Ice Age. the Würm or Weichsel Glaciation, the maximum extent of the glaciers occurred at the end of the Ice Age, as late as 20.000 years ago. The main retreat phases during deglaciation were marked as distinct ice marginal zones and dated between 20,000 and 9,000 BP.

A Discussion of Atmospheric Circulation During the Last Ice Age

1971 ◽  
Vol 1 (3) ◽  
pp. 415-418 ◽  
Author(s):  
R.G. Barry ◽  
J.D. Ives ◽  
J.T. Andrews
Keyword(s):  
Atmospheric Circulation ◽  
Ice Age ◽  
Last Ice Age

scholarly journals Arctic Ocean stratification set by sea level and freshwater inputs since the last ice age

2021 ◽  
Author(s):  
Jesse R. Farmer ◽  
Daniel M. Sigman ◽  
Julie Granger ◽  
Ona M. Underwood ◽  
François Fripiat ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Surface Waters ◽  
Ice Age ◽  
The Arctic ◽  
Bering Strait ◽  
Central Arctic Ocean ◽  
Phytoplankton Productivity ◽  
Nitrate Consumption ◽  
Western Arctic ◽  
Last Ice Age

AbstractSalinity-driven density stratification of the upper Arctic Ocean isolates sea-ice cover and cold, nutrient-poor surface waters from underlying warmer, nutrient-rich waters. Recently, stratification has strengthened in the western Arctic but has weakened in the eastern Arctic; it is unknown if these trends will continue. Here we present foraminifera-bound nitrogen isotopes from Arctic Ocean sediments since 35,000 years ago to reconstruct past changes in nutrient sources and the degree of nutrient consumption in surface waters, the latter reflecting stratification. During the last ice age and early deglaciation, the Arctic was dominated by Atlantic-sourced nitrate and incomplete nitrate consumption, indicating weaker stratification. Starting at 11,000 years ago in the western Arctic, there is a clear isotopic signal of Pacific-sourced nitrate and complete nitrate consumption associated with the flooding of the Bering Strait. These changes reveal that the strong stratification of the western Arctic relies on low-salinity inflow through the Bering Strait. In the central Arctic, nitrate consumption was complete during the early Holocene, then declined after 5,000 years ago as summer insolation decreased. This sequence suggests that precipitation and riverine freshwater fluxes control the stratification of the central Arctic Ocean. Based on these findings, ongoing warming will cause strong stratification to expand into the central Arctic, slowing the nutrient supply to surface waters and thus limiting future phytoplankton productivity.

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