Middle Eocene—Lower Oligocene Climatic Transition and Planktonic Foraminiferal Biostratigraphy at DSDP Sites 219 and 237, Arabian Sea and Western Tropical Indian Ocean

2018 ◽  
pp. 263-291
Author(s):  
Prabha Kalia ◽  
L. R. Sahu
Keyword(s):  
Indian Ocean ◽  
Arabian Sea ◽  
Middle Eocene ◽  
Tropical Indian Ocean ◽  
Lower Oligocene ◽  
Climatic Transition ◽  
Foraminiferal Biostratigraphy

Summer Rainfall Variability in Low-Latitude Highlands of China and Subtropical Indian Ocean Dipole

2014 ◽  
Vol 27 (2) ◽  
pp. 880-892 ◽  
Author(s):  
Jie Cao ◽  
Ping Yao ◽  
Lin Wang ◽  
Kui Liu
Keyword(s):  
Water Vapor ◽  
Indian Ocean ◽  
Arabian Sea ◽  
Tropical Indian Ocean ◽  
Summer Rainfall ◽  
Wind Component ◽  
Vertical Circulation ◽  
Low Latitude ◽  
Divergent Wind ◽  
Rainfall Variations

Abstract Based on reanalysis and observational datasets, this study proposes a reasonable mechanism for summer rainfall variations over the low-latitude highlands (LLH) of China, in which a subtropical Indian Ocean dipole (SIOD)-like pattern is the key external thermal forcing. In summers with a positive SIOD-like pattern, sea surface temperature (SST) anomalies may lead to lower-tropospheric divergence over the tropical Indian Ocean and convergence over the subtropical southwestern Indian Ocean and Arabian Sea. The convergence over the Arabian Sea can induce easterly anomalies of the divergent wind component off the eastern coast of the Bay of Bengal (BOB), while the divergence over the tropical Indian Ocean can change the interhemispheric vertical circulation and produce a descending motion over the same area and cyclonic anomalies in the rotational wind component over the Indian peninsula. The combined effect of the divergent and rotational wind anomalies and enhanced interhemispheric vertical circulation facilitates easterly anomalies and weakens climatological water vapor flux to the northern BOB. Therefore, anomalous water vapor divergence and less precipitation are observed over the LLH. In summers with a negative SIOD-like pattern, the situation is approximately the same but with opposite polarity and a weaker role of the divergent wind component. Further analyses indicate that the summertime SIOD-like pattern can be traced to preceding seasons, especially in positive SIOD-like years. The SST–wind–evaporation feedback mechanism could account for maintenance of the SIOD-like pattern. These results provide efficient prediction potential for summer rainfall variations over the LLH.

The monsoon imprint during the ‘atypical’ MIS 13 as seen through north and equatorial Indian Ocean records

2011 ◽  
Vol 76 (2) ◽  
pp. 285-293 ◽  
Author(s):  
Thibaut Caley ◽  
Bruno Malaizé ◽  
Franck Bassinot ◽  
Steven C. Clemens ◽  
Nicolas Caillon ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Arabian Sea ◽  
Indian Monsoon ◽  
Equatorial Indian Ocean ◽  
Tropical Indian Ocean ◽  
Monsoon Precipitation ◽  
Low Salinity ◽  
Tropical Areas ◽  
Paleoclimate Records ◽  
Monsoon Winds

AbstractPrevious studies have suggested that Marine Isotope Stage (MIS) 13, recognized as atypical in many paleoclimate records, is marked by the development of anomalously strong summer monsoons in the northern tropical areas. To test this hypothesis, we performed a multi-proxy study on three marine records from the tropical Indian Ocean in order to reconstruct and analyse changes in the summer Indian monsoon winds and precipitations during MIS 13. Our data confirm the existence of a low-salinity event during MIS 13 in the equatorial Indian Ocean but we argue that this event should not be considered as “atypical”. Taking only into account a smaller precession does not make it possible to explain such precipitation episode. However, when considering also the larger obliquity in a more complete orbitally driven monsoon “model,” one can successfully explain this event. In addition, our data suggest that intense summer monsoon winds, although not atypical in strength, prevailed during MIS 13 in the western Arabian Sea. These strong monsoon winds, transporting important moisture, together with the effect of insolation and Eurasian ice sheet, are likely one of the factors responsible for the intense monsoon precipitation signal recorded in China loess, as suggested by model simulations.

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