Atmospheric Circulation during the Onset and Maximum Development of the Wisconsin/Würm Ice Age

1974 ◽  
pp. 349-358 ◽  
Author(s):  
Hubert Horace Lamb
Keyword(s):  
Atmospheric Circulation ◽  
Ice Age ◽  
Maximum Development

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.

Reduced Atlantic Storminess during Last Glacial Maximum: Evidence from a Coupled Climate Model

2008 ◽  
Vol 21 (14) ◽  
pp. 3561-3579 ◽  
Author(s):  
Camille Li ◽  
David S. Battisti
Keyword(s):  
Atmospheric Circulation ◽  
Last Glacial Maximum ◽  
Climate Model ◽  
Glacial Maximum ◽  
Ice Age ◽  
Atlantic Sector ◽  
Eddy Activity ◽  
Last Glacial ◽  
Proxy Records ◽  
Paleoclimate Proxy

Abstract The Last Glacial Maximum (LGM), 21 000 yr before present, was the time of maximum land ice extent during the last ice age. A recent simulation of the LGM climate by a state-of-the-art fully coupled global climate model is shown to exhibit strong, steady atmospheric jets and weak transient eddy activity in the Atlantic sector compared to today’s climate. In contrast, previous work based on uncoupled atmospheric model simulations has shown that the LGM jets and eddy activity in the Atlantic sector are similar to those observed today, with the main difference being a northeastward extension of their maxima. The coupled model simulation is shown to agree more with paleoclimate proxy records and thus is taken as the more reliable representation of LGM climate. The existence of this altered atmospheric circulation state during LGM in the model has implications for understanding the stability of glacial climates, for the possibility of multiple atmospheric circulation regimes, and for the interpretation of paleoclimate proxy records.

Geological records of changes in wind regime over south Greenland since the Medieval Warm Period: a tentative reconstruction

Polar Record ◽  
2009 ◽  
Vol 45 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Antoon Kuijpers ◽  
Naja Mikkelsen
Keyword(s):  
Atmospheric Circulation ◽  
Medieval Warm Period ◽  
Warm Period ◽  
Ice Age ◽  
East Greenland Current ◽  
Aeolian Deposits ◽  
New Information ◽  
North Atlantic Climate ◽  
Wind Activity ◽  
Marine Data

ABSTRACTPublished marine sediment core records and new information from terrestrial aeolian deposits from the surroundings of Igaliku Fjord, south Greenland, have been used for a tentative reconstruction of multi-decadal to centennial scale changes in the intensity of regional atmospheric circulation since the Medieval Warm Period. The marine data show that aeolian activity over southern Greenland was generally enhanced in the Medieval Warm Period between c. AD 900 and c. AD 1300. The preliminary data from the onshore aeolian deposits suggest that wind activity was strongest after AD 1000, reaching a peak close to AD 1300, after which atmospheric circulation intensity decreased. A comparison with the marine data shows that this decrease coincides with increased advection of Polar Water by the East Greenland Current at the beginning of the Little Ice Age. The aeolian sediment record suggests foehn wind activity displaying multi-decadal oscillations in the range of known north Atlantic climate oscillations. The intensity of erosional processes in south Greenland has previously often been attributed to farming activities initiated after AD 1000 by the Norse who disappeared a few hundred years later. Our findings suggest, however, that erosion in this area is mainly related to marked variations in wind strength.

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.

scholarly journals Holocene fluvial response to climate change and human activities; Burgundy, France.

2002 ◽  
Vol 81 (3-4) ◽  
pp. 417-430 ◽  
Author(s):  
E.C. Straffin ◽  
M.D. Blum
Keyword(s):  
Atmospheric Circulation ◽  
Climatic Variability ◽  
Sediment Supply ◽  
Ice Age ◽  
Agricultural Activity ◽  
Vegetative Cover ◽  
Analogue Model ◽  
Alluvial Deposits ◽  
Modern Analogue ◽  
Tributary System

AbstractAlluvial deposits of the Loire/Arroux trunk/tributary system record distinct, synchronous episodes of regional fluvial adjustment. Changes in facies and depositional style through time can be interpreted with a modern analogue model that relates vegetative cover/human influence with sediment supply, and modes of atmospheric circulation with the paths and styles of storms that drive variable discharge regimes across western Europe.Zonal atmospheric circulation results in a Mediterranean style climate over southern Burgundy, producing dry conditions punctuated by infrequent, large floods. Episodic overbank sedimentation and the burial of thin paleosols in sandy overbank facies is indicative of this style of fluvial activity, ca 1300 years BP. Humans may have increased the available volume of fine grained sediment at this times through increased agricultural activity along valley axes, however facies match that expected from a ‘flashy’ discharge regime.In contrast, meridional circulation patterns result in a maritime style climate over southern Burgundy, with the intrusion of storms, moist conditions and frequent, moderate magnitude discharges. Wide, deep channels, thick channel facies and thin overbank facies are indicative of this style of fluvial activity, recorded in deposits dating to ca 4050 to 3200 years BP. Strong meridional conditions and extreme climatic variability during the Little Ice Age resulted in very large discharges that straightened and widened channels, while scouring and obscuring older terraces (ca 500 years BP). Deposition over the last two centuries is related to increasingly zonal circulation and infrequent, large (over-bank) floods. Changes in fluvial dynamics over the last 300 years can be attributed primarily to climatic control, as there has been very little change in land-use over that period.

scholarly journals Defining the Little Ice Age

2010 ◽  
Vol 6 (5) ◽  
pp. 2159-2175 ◽  
Author(s):  
Ø. Paasche ◽  
J. Bakke
Keyword(s):  
Atmospheric Circulation ◽  
Little Ice Age ◽  
Southern Oscillation ◽  
West African Monsoon ◽  
West African ◽  
Ice Age ◽  
Northern Annular Mode ◽  
Wide Range ◽  
Low Latitudes ◽  
Harsh Climate

Abstract. The "Little Ice Age" (LIA) is possibly the best-documented climatic anomaly of the past. A wide range of datasets portrays a harsh climate that worsened living conditions, primarily in terms of cooler temperatures, for people across Europe sometime during the last millennium. Regardless of the vast amount of data covering the LIA, there is presently no consensus concerning its spatial manifestation (was it regional or global?), its temporal constraints (when did it start and end?), or the broad-scale dynamics associated with it (what mechanisms did it involve?), although there is no shortage of suggestions. Based on a new compilation of data reflecting atmospheric circulation at both high and low latitudes, we show that the LIA lasted for roughly 400 years (∼1400–1800 AD). During this period at least four major atmospheric circulation systems on Earth co-varied on decadal to centennial timescales: Northern Annular Mode (NAM), Intertropical Convergence Zone (ITCZ), El Nino-Southern Oscillation (ENSO) and West African Monsoon (WAM). This pattern of convergence suggests that a strong coupling between these circulation systems was an important pre-condition for the realisation of the LIA.

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.

scholarly journals Centennial-scale shifts in the position of the Southern Hemisphere westerly wind belt over the past millennium

2013 ◽  
Vol 9 (3) ◽  
pp. 3125-3174 ◽  
Author(s):  
B. G. Koffman ◽  
K. J. Kreutz ◽  
D. J. Breton ◽  
E. J. Kane ◽  
D. A. Winski ◽  
...  
Keyword(s):  
Particle Size ◽  
Atmospheric Circulation ◽  
Southern Hemisphere ◽  
Ice Core ◽  
Hadley Cell ◽  
Ice Age ◽  
Westerly Wind ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Local Dust

Abstract. We present the first high-resolution (sub-annual) dust particle dataset from West Antarctica, developed from the West Antarctic Ice Sheet (WAIS) Divide deep ice core (79.468° S, 112.086° W), and use it to reconstruct past atmospheric circulation. We find a background dust flux of ∼4 mg m−2 yr−1 and a mode particle size of 5–8 μm diameter. Through comparison with other Antarctic ice core particle records, we observe that coastal and lower-elevation sites have higher dust fluxes and coarser particle size distributions (PSDs) than sites on the East Antarctic plateau, suggesting input from local dust sources at lower elevations and sites closer to the coast. In order to explore the use of the WAIS Divide dust PSD as a proxy for past atmospheric circulation, we make quantitative comparisons between mid-latitude zonal wind speed and the dust size (coarse particle percentage, CPP) record, finding significant positive interannual relationships. Using our CPP record, and through comparison with spatially distributed climate reconstructions from the Southern Hemisphere (SH) middle and high latitudes, we infer latitudinal shifts in the position of the SH westerly wind belt during the Medieval Climate Anomaly (MCA; ∼950–1350 C.E.) and Little Ice Age (LIA; ∼1400–1850 C.E.) climate intervals. We suggest that the SH westerlies occupied a more southerly position during the MCA, and shifted equatorward at the onset of the LIA (∼ 1430 C.E.) due to cooler surface temperatures and a contraction of the SH Hadley cell.

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