scholarly journals Lake-level changes and hominin occupations in the arid Turkana Basin during volcanic closure of the Omo River outflows to the Indian Ocean – Response to comments by Schuster and Nutz, Quaternary Research 92(2), pp. 598–600

2019 ◽  
Vol 92 (2) ◽  
pp. 601-604 ◽  
Author(s):  
Xavier Boës ◽  
Sandrine Prat ◽  
Vincent Arrighi ◽  
Craig Feibel ◽  
Bereket Haileab ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Lake Level ◽  
Turkana Basin ◽  
Lake Level Changes ◽  
Ocean Response ◽  
The Indian Ocean ◽  
Omo River

scholarly journals Lake-level changes and hominin occupations in the arid Turkana basin during volcanic closure of the Omo River outflows to the Indian Ocean

2018 ◽  
Vol 91 (2) ◽  
pp. 892-909 ◽  
Author(s):  
Xavier Boës ◽  
Sandrine Prat ◽  
Vincent Arrighi ◽  
Craig Feibel ◽  
Bereket Haileab ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Lake Sediments ◽  
Inductively Coupled Plasma ◽  
Optical Emission ◽  
Sedimentary Facies ◽  
Emission Spectrometry ◽  
Lake Turkana ◽  
Inductively Coupled ◽  
The Indian Ocean ◽  
Omo River

AbstractIn the East African Rift, the western margin of Lake Turkana (northern Kenya) exposes Mio-Plio-Pleistocene lake sediments with dated volcanic horizons constraining basin dynamics at the astronomical time scale. Since the late Pliocene, coastal archaeological sites have formed within the lacustrine dynamics. Here, lake levels are reconstructed from 2.4 to 1.7 Ma using sedimentary facies and water/depth-controlled sediment association. The lacustrine stratigraphy is measured with a total station, and cyclostratigraphy is derived from tephrochronology. The water depths are evaluated from paleochemical properties of lake sediments analyzed by inductively coupled plasma optical emission spectrometry and inductively coupled plasma mass spectrometry. Our reconstruction highlights that Lake Turkana rose during 100 ka insolation/eccentricity maxima periods in response to higher monsoonal inputs of the Omo River. However, Lake Turkana also expanded through an insolation minimum at 2.17–1.95 Ma. This asynchronous lake phase coincides with volcanic closure of the Omo River and Lake Turkana outflow sill to the east and the Indian Ocean. An archaeological hiatus occurs during this endorheic lake phase, and alkalinity increases at the beginning of the hiatus. The lake rose again during insolation/eccentricity maxima at 1.9–1.7 Ma, and a new outflow sill opened to the west and the Nile basin. Hominin coastal occupations return during this exorheic/freshwater lake phase.

Understanding the Indian Ocean response to double CO2 forcing in a coupled model

2015 ◽  
Vol 65 (7) ◽  
pp. 1037-1046 ◽  
Author(s):  
Wei Liu ◽  
Jian Lu ◽  
Shang-Ping Xie
Keyword(s):  
Indian Ocean ◽  
Coupled Model ◽  
Ocean Response ◽  
The Indian Ocean ◽  
Co2 Forcing

Influence of the Indian Ocean Dipole on Atmospheric Subseasonal Variability

2005 ◽  
Vol 18 (18) ◽  
pp. 3891-3909 ◽  
Author(s):  
Toshiaki Shinoda ◽  
Weiqing Han
Keyword(s):  
Indian Ocean ◽  
Zonal Wind ◽  
Indian Ocean Dipole ◽  
Interannual Variation ◽  
Near Surface ◽  
Subseasonal Variability ◽  
Ocean Response ◽  
The Indian Ocean ◽  
Wind Activity ◽  
Sst Gradient

Abstract The relationship between atmospheric subseasonal variability and interannual variation of SST over the tropical Indian Ocean is examined using winds and humidity from the NCEP–NCAR reanalysis, outgoing longwave radiation (OLR), and the monthly SST analysis. The primary focus is on whether and how the subseasonal variability is related to the zonal dipole structure of SST, which peaks during boreal fall. The level of subseasonal wind activity is measured by standard deviation of bandpass-filtered zonal wind fields on the 6–30- and 30–90-day time scales. During boreal fall (September–November), the interannual variation of 6–30-day (submonthly) near-surface zonal wind activity in the central and eastern equatorial Indian Ocean is highly correlated with the large-scale zonal SST gradient. The intensity of submonthly variability is largely reduced during positive dipole years. A significant reduction of intraseasonal (30–90-day) wind activity is also evident during large dipole events. However, the correlation with the zonal SST gradient is much weaker than that of submonthly variability. The mechanism by which the Indian Ocean dipole influences equatorial submonthly winds is investigated based on a cross-correlation analysis of OLR and winds. During negative dipole years, submonthly convection is active in the southeast Indian Ocean where the anomalous convergence of surface moisture associated with dipole events is at its maximum. The submonthly convection in this region is often associated with a cyclonic circulation, and these disturbances propagate westward. Consequently, equatorial westerlies and northwesterly winds near the coast of Sumatra are generated. During positive dipole years, submonthly convective activity is highly reduced in the southeast Indian Ocean, and thus no equatorial westerly is generated. Ocean response to submonthly disturbances is examined using OGCM experiments forced with winds from the NCEP–NCAR reanalysis. Results suggest that submonthly winds can generate significant upper-ocean response, including strong eastward surface currents near the equator and sea surface height anomalies along the coast of Sumatra where the large SST anomalies associated with dipole events are observed.

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