scholarly journals Were springline carbonates in the Kurkur-Dungul area (Southern Egypt) deposited during glacial periods?

2020 ◽  
pp. jgs2020-147
Author(s):  
Sándor Kele ◽  
Emad S. Sallam ◽  
Enrico Capezzuoli ◽  
Mike Rogerson ◽  
Hamdalla Wanas ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Sea Level ◽  
Warm Pool ◽  
Source Water ◽  
Indonesian Throughflow ◽  
Orbital Forcing ◽  
Western Margin ◽  
The Indian Ocean ◽  
Glacial Periods ◽  
Aquifer Flow

The tufa deposits in the Kurkur–Dungul area, southern Egypt, date from marine isotope stage (MIS) 11 to MIS 1. Springs across the region were active during glacial periods (with sea level below –50 m), reflecting changed atmospheric circulation over the Indian Ocean, as well as peak interglacial periods. During times of low sea level, reduced Indonesian throughflow promoted formation of an Indian Ocean Warm Pool, and anomalous rainfall on its western margin. We suggest Egypt lies at the intersection of westerly (“maghrebian”) and easterly (“mashriqian”) rainfall provinces, which show different timing with relation to orbital forcing and different source water regions. Tufa-growth periods are therefore not mechanistically linked to “humid periods” or “sapropel events” identified elsewhere. Stable isotope and TΔ47 data are also inconsistent with these spring systems being part of a larger system spanning northern Africa, and lack a clear interaction between northern hemisphere heating and mid-latitude rainfall. We also follow previous authors in concluding that formation of springline deposit formation was likely delayed compared to rainfall, due to aquifer flow distances. This delay is unlikely sufficient to explain why rainfall is out of phase movements of the monsoon belts, but may complicate interpretation of these records.

Impact of the barotropic tides on the seasonal Indonesian Throughflow 

2021 ◽  
Author(s):  
Oceane Richet ◽  
Bernadette Sloyan ◽  
Bea Pena-Molino ◽  
Maxim Nikurashin
Keyword(s):  
Indian Ocean ◽  
Thermohaline Circulation ◽  
Vertical Mixing ◽  
Warm Pool ◽  
Ocean Basin ◽  
Indonesian Throughflow ◽  
Indonesian Seas ◽  
Pacific Waters ◽  
The Indian Ocean ◽  
The Impact

<p>The Indonesian seas play a fundamental role in the coupled climate system, featuring the only tropical exchange between ocean basins in the global thermohaline circulation. The Indonesian Throughflow (ITF) carries Pacific Ocean warm pool waters through the Indonesian Seas, where they are cooled and freshened. The incoming Pacific waters are strongly modified via vertical mixing driven by numerous ocean processes and ocean-atmosphere fluxes. The result is a unique water mass that can be tracked across the Indian Ocean basin and beyond. With our high-resolution regional model of the Indonesian Seas, designed with the MITgcm, we focus our study on the impact of the barotropic tides on the ITF. In fact, the strong tides coming from the Pacific and Indian Oceans enter in the Indonesian Seas through narrow straits and interact with the complex topography of the region (sills, islands, deep seas). This interaction between the tides and the topography impacts directly the ITF by modifying the transport toward the Indian Ocean.</p>

Intraseasonal-to-Interannual Variability of South Indian Ocean Sea Level and Thermocline: Remote versus Local Forcing

2012 ◽  
Vol 42 (4) ◽  
pp. 602-627 ◽  
Author(s):  
Laurie L. Trenary ◽  
Weiqing Han
Keyword(s):  
Indian Ocean ◽  
Interannual Variability ◽  
Sea Level ◽  
Time Scales ◽  
Ekman Pumping ◽  
Remote Forcing ◽  
South Indian ◽  
The Pacific ◽  
The Indian Ocean ◽  
Thermocline Variability

Abstract The relative importance of local versus remote forcing on intraseasonal-to-interannual sea level and thermocline variability of the tropical south Indian Ocean (SIO) is systematically examined by performing a suite of controlled experiments using an ocean general circulation model and a linear ocean model. Particular emphasis is placed on the thermocline ridge of the Indian Ocean (TRIO; 5°–12°S, 50°–80°E). On interannual and seasonal time scales, sea level and thermocline variability within the TRIO region is primarily forced by winds over the Indian Ocean. Interannual variability is largely caused by westward propagating Rossby waves forced by Ekman pumping velocities east of the region. Seasonally, thermocline variability over the TRIO region is induced by a combination of local Ekman pumping and Rossby waves generated by winds from the east. Adjustment of the tropical SIO at both time scales generally follows linear theory and is captured by the first two baroclinic modes. Remote forcing from the Pacific via the oceanic bridge has significant influence on seasonal and interannual thermocline variability in the east basin of the SIO and weak impact on the TRIO region. On intraseasonal time scales, strong sea level and thermocline variability is found in the southeast tropical Indian Ocean, and it primarily arises from oceanic instabilities. In the TRIO region, intraseasonal sea level is relatively weak and results from Indian Ocean wind forcing. Forcing over the Pacific is the major cause for interannual variability of the Indonesian Throughflow (ITF) transport, whereas forcing over the Indian Ocean plays a larger role in determining seasonal and intraseasonal ITF variability.

scholarly journals Previously unidentified Indonesian Throughflow pathways and freshening in the Indian Ocean during recent decades

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Salvienty Makarim ◽  
Janet Sprintall ◽  
Zhiyu Liu ◽  
Weidong Yu ◽  
Agus Santoso ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Indonesian Throughflow ◽  
The Indian Ocean

scholarly journals Decadal Variability of the Indian and Pacific Walker Cells since the 1960s: Do They Covary on Decadal Time Scales?

2017 ◽  
Vol 30 (21) ◽  
pp. 8447-8468 ◽  
Author(s):  
Weiqing Han ◽  
Gerald A. Meehl ◽  
Aixue Hu ◽  
Jian Zheng ◽  
Jessica Kenigson ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Decadal Variability ◽  
Tropical Indian Ocean ◽  
Warm Pool ◽  
Past Century ◽  
The Pacific ◽  
Decadal Variations ◽  
Long Term Trends ◽  
The Indian Ocean ◽  
The 1960S

Previous studies have investigated the centennial and multidecadal trends of the Pacific and Indian Ocean Walker cells (WCs) during the past century, but have obtained no consensus owing to data uncertainties and weak signals of the long-term trends. This paper focuses on decadal variability (periods of one to few decades) by first documenting the variability of the WCs and warm-pool convection, and their covariability since the 1960s, using in situ and satellite observations and reanalysis products. The causes for the variability and covariability are then explored using a Bayesian dynamic linear model, which can extract nonstationary effects of climate modes. The warm-pool convection exhibits apparent decadal variability, generally covarying with the Indian and Pacific Ocean WCs during winter (November–April) with enhanced convection corresponding to intensified WCs, and the Indian–Pacific WCs covary. During summer (May–October), the warm-pool convection still highly covaries with the Pacific WC but does not covary with the Indian Ocean WC, and the Indian–Pacific WCs are uncorrelated. The wintertime coherent variability results from the vital influence of ENSO decadal variation, which reduces warm-pool convection and weakens the WCs during El Niño–like conditions. During summer, while ENSO decadal variability still dominates the Pacific WC, decadal variations of ENSO, the Indian Ocean dipole, Indian summer monsoon convection, and tropical Indian Ocean SST have comparable effects on the Indian Ocean WC overall, with monsoon convection having the largest effect since the 1990s. The complex causes for the Indian Ocean WC during summer result in its poor covariability with the Pacific WC and warm-pool convection.

scholarly journals Forcing of the Indian Ocean Dipole on the Interannual Variations of the Tropical Pacific Ocean: Roles of the Indonesian Throughflow

2011 ◽  
Vol 24 (14) ◽  
pp. 3593-3608 ◽  
Author(s):  
Dongliang Yuan ◽  
Jing Wang ◽  
Tengfei Xu ◽  
Peng Xu ◽  
Zhou Hui ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Indian Ocean ◽  
Indian Ocean Dipole ◽  
Tropical Pacific ◽  
Equatorial Pacific ◽  
Indonesian Throughflow ◽  
Tropical Pacific Ocean ◽  
Equatorial Pacific Ocean ◽  
The Indian Ocean ◽  
The Tropical Pacific

Abstract Controlled numerical experiments using ocean-only and ocean–atmosphere coupled general circulation models show that interannual sea level depression in the eastern Indian Ocean during the Indian Ocean dipole (IOD) events forces enhanced Indonesian Throughflow (ITF) to transport warm water from the upper-equatorial Pacific Ocean to the Indian Ocean. The enhanced transport produces elevation of the thermocline and cold subsurface temperature anomalies in the western equatorial Pacific Ocean, which propagate to the eastern equatorial Pacific to induce significant coupled evolution of the tropical Pacific oceanic and atmospheric circulation. Analyses suggest that the IOD-forced ITF transport anomalies are about the same amplitudes as those induced by the Pacific ENSO. Results of the coupled model experiments suggest that the anomalies induced by the IOD persist in the equatorial Pacific until the year following the IOD event, suggesting the importance of the oceanic channel in modulating the interannual climate variations of the tropical Pacific Ocean at the time lag beyond one year.

Natural decadal sea-level variability in the Indian Ocean: lessons from CMIP models

2019 ◽  
Vol 53 (9-10) ◽  
pp. 5653-5673
Author(s):  
A. G. Nidheesh ◽  
Matthieu Lengaigne ◽  
Jérôme Vialard ◽  
Takeshi Izumo ◽  
A. S. Unnikrishnan ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Sea Level ◽  
Sea Level Variability ◽  
The Indian Ocean
Sign in / Sign up

Export Citation Format

Share Document