High-Latitude Forcing of the South American Summer Monsoon During the Last Glacial

Science ◽  
2012 ◽  
Vol 335 (6068) ◽  
pp. 570-573 ◽  
Author(s):  
L. C. Kanner ◽  
S. J. Burns ◽  
H. Cheng ◽  
R. L. Edwards
Keyword(s):  
Summer Monsoon ◽  
High Latitude ◽  
South American ◽  
The South ◽  
Last Glacial ◽  
The Last Glacial

scholarly journals Centennial-scale precipitation anomalies in the southern Altiplano (18° S) suggest an extratropical driver for the South American summer monsoon during the late Holocene

2019 ◽  
Vol 15 (5) ◽  
pp. 1845-1859 ◽  
Author(s):  
Ignacio A. Jara ◽  
Antonio Maldonado ◽  
Leticia González ◽  
Armand Hernández ◽  
Alberto Sáez ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Large Scale ◽  
Southern Oscillation ◽  
Atlantic Coast ◽  
Austral Summer ◽  
High Elevation ◽  
South American ◽  
Tropical Andes ◽  
The South ◽  
Precipitation Anomalies

Abstract. Modern precipitation anomalies in the Altiplano, South America, are closely linked to the strength of the South American summer monsoon (SASM), which is influenced by large-scale climate features sourced in the tropics such as the Intertropical Convergence Zone (ITCZ) and El Niño–Southern Oscillation (ENSO). However, the timing, direction, and spatial extent of precipitation changes prior to the instrumental period are still largely unknown, preventing a better understanding of the long-term drivers of the SASM and their effects over the Altiplano. Here we present a detailed pollen reconstruction from a sedimentary sequence covering the period between 4500 and 1000 cal yr BP in Lago Chungará (18∘ S; 4570 m a.s.l.), a high-elevation lake on the southwestern margin of the Altiplano where precipitation is delivered almost exclusively during the mature phase of the SASM over the austral summer. We distinguish three well-defined centennial-scale anomalies, with dry conditions between 4100–3300 and 1600–1000 cal yr BP and a conspicuous humid interval between 2400 and 1600 cal yr BP, which resulted from the weakening and strengthening of the SASM, respectively. Comparisons with other climate reconstructions from the Altiplano, the Atacama Desert, the tropical Andes, and the southwestern Atlantic coast reveal that – unlike modern climatological controls – past precipitation anomalies at Lago Chungará were largely decoupled from north–south shifts in the ITCZ and ENSO. A regionally coherent pattern of centennial-scale SASM variations and a significant latitudinal gradient in precipitation responses suggest the contribution of an extratropical moisture source for the SASM, with significant effects on precipitation variability in the southern Altiplano.

Baetisca (Ephemeroptera: Baetiscidae) from the western interior of Canada with notes on the life cycle

1972 ◽  
Vol 50 (7) ◽  
pp. 1015-1017 ◽  
Author(s):  
D. M. Lehmkuhl
Keyword(s):  
Life Cycle ◽  
Drainage System ◽  
The South ◽  
Glacial Retreat ◽  
Last Glacial ◽  
The North ◽  
South Saskatchewan River ◽  
Dispersal Routes ◽  
The Last Glacial

The distributions of Baetisca obesa (Say) and B. bajkovi Neave in Canada are extended west to Saskatchewan and Alberta. Generic features of adults and nymphs and specific characters of the nymphs of the two species are illustrated. In the South Saskatchewan River nymphs of B. bajkovi hatch from the egg in August and September, they pass the winter under the ice, and adults emerge the following June and July. The Hudson's Bay drainage system was probably invaded by these species from the Mississippi drainage system during the last glacial retreat, since at various times dispersal routes in the form of rivers have been present from the southern refugium for migration to the north.

scholarly journals Possible impact of the Atlantic Multidecadal Oscillation on the South American summer monsoon

2009 ◽  
Vol 36 (21) ◽  
Author(s):  
Cristiano M. Chiessi ◽  
Stefan Mulitza ◽  
Jürgen Pätzold ◽  
Gerold Wefer ◽  
José A. Marengo
Keyword(s):  
Summer Monsoon ◽  
Atlantic Multidecadal Oscillation ◽  
South American ◽  
The South

scholarly journals Origin of last-glacial loess in the western Yukon-Tanana Upland, central Alaska, USA

2018 ◽  
Vol 89 (3) ◽  
pp. 797-819 ◽  
Author(s):  
Daniel R. Muhs ◽  
Jeffrey S. Pigati ◽  
James R. Budahn ◽  
Gary L. Skipp ◽  
E. Arthur Bettis ◽  
...  
Keyword(s):  
Drainage Basin ◽  
Coarse Grained ◽  
Geochemical Data ◽  
Glacial Period ◽  
The South ◽  
Last Glacial Period ◽  
Last Glacial ◽  
Recent Climate ◽  
Loess Deposits ◽  
The Last Glacial

AbstractLoess is widespread over Alaska, and its accumulation has traditionally been associated with glacial periods. Surprisingly, loess deposits securely dated to the last glacial period are rare in Alaska, and paleowind reconstructions for this time period are limited to inferences from dune orientations. We report a rare occurrence of loess deposits dating to the last glacial period, ~19 ka to ~12 ka, in the Yukon-Tanana Upland. Loess in this area is very coarse grained (abundant coarse silt), with decreases in particle size moving south of the Yukon River, implying that the drainage basin of this river was the main source. Geochemical data show, however, that the Tanana River valley to the south is also a likely distal source. The occurrence of last-glacial loess with sources to both the south and north is explained by both regional, synoptic-scale winds from the northeast and opposing katabatic winds that could have developed from expanded glaciers in both the Brooks Range to the north and the Alaska Range to the south. Based on a comparison with recent climate modeling for the last glacial period, seasonality of dust transport may also have played a role in bringing about contributions from both northern and southern sources.

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