Sea surface salinity dipole mode in the tropical Indian Ocean and its relationship with Indo-Pacific climate  

2021 ◽  
Author(s):  
Yuhong Zhang ◽  
Yan Du ◽  
Qiwei Sun
Keyword(s):  
Indian Ocean ◽  
Walker Circulation ◽  
Tropical Indian Ocean ◽  
Sea Surface Salinity ◽  
Thermocline Depth ◽  
Surface Salinity ◽  
The Pacific ◽  
The Indian Ocean ◽  
Atmospheric Channel ◽  
The Western Pacific

<p>An atmospheric channel with the monsoon circulation system and the Walker circulation and an ocean channel with Indonesian through-flow, connect the tropical Indian Ocean and the Pacific, which strongly modulate the Indo-Pacific climate change on different time scales. The atmospheric channel transports 0.35 Sv water vapor from the Indian Ocean to the Pacific on the mean state, while the Indonesia throughflow transports ~15 Sv of freshwater from the western Pacific to the Indian Ocean. These two aspects of freshwater transportation play an important role in maintaining the salinity balance in the tropical Indian Ocean (TIO). On the interannual-decadal time scale, a sea surface salinity dipole mode has been revealed in the tropical Indian Ocean (S-IOD) with salinity anomalies in the central equator and the southeastern TIO is opposite, corresponding to significant wind anomaly along the equator and precipitation and thermocline depth anomalies in the southeastern TIO. The ocean advection forced by wind anomalies along the equator and precipitation and thermocline depth anomalies in the southeastern TIO dominating the SSS variations of the S-IOD, respectively. The modulation of the Indo-Pacific Walker Circulation and its related ocean wave processes transported from the western Pacific through the waveguide in the Indonesian Seas are main factors for the development of S-IOD and its variability, which is forced by the Interdecadal Pacific Oscillation (IPO). Further analyses indicate that the long-term trend of SSS in the global ocean with the salty regions getting saltier and fresh regions getting fresher is modulated by the internal variability associated with the IPO, with the most significant regions in the western tropical Pacific and the southeastern Indian Ocean. Specifically, the IPO leads to a ~40% offset of SSS radiative-forced trend in the western tropical Pacific and ~170% enhancement of the trend in the southeastern Indian Ocean since the mid-20th century.      </p>

scholarly journals Satellite and Argo Observed Surface Salinity Variations in the Tropical Indian Ocean and Their Association with the Indian Ocean Dipole Mode

2015 ◽  
Vol 28 (2) ◽  
pp. 695-713 ◽  
Author(s):  
Yan Du ◽  
Yuhong Zhang
Keyword(s):  
Indian Ocean ◽  
Ocean Circulation ◽  
Indian Ocean Dipole ◽  
Coastal Upwelling ◽  
Tropical Indian Ocean ◽  
Sea Surface Salinity ◽  
The South ◽  
Surface Salinity ◽  
Indian Ocean Dipole Mode ◽  
The Indian Ocean

Abstract This study investigates sea surface salinity (SSS) variations in the tropical Indian Ocean (IO) using the Aquarius/Satelite de Aplicaciones Cientificas-D (SAC-D) and the Soil Moisture and Ocean Salinity (SMOS) satellite data and the Argo observations during July 2010–July 2014. Compared to the Argo observations, the satellite datasets generally provide SSS maps with higher space–time resolution, particularly in the regions where Argo floats are sparse. Both Aquarius and SMOS well captured the SSS variations associated with the Indian Ocean dipole (IOD) mode. Significant SSS changes occurred in the central equatorial IO, along the Java–Sumatra coast, and south of the equatorial IO, due to ocean circulation variations. During the negative IOD events in 2010, 2013, and 2014, westerly wind anomalies strengthened along the equator, weakening coastal upwelling off Java and Sumatra and decreasing SSS. South of the equatorial IO, an anomalous cyclonic gyre changed the tropical circulation, which favored the eastward high-salinity tongue along the equator and the westward low-saline tongue in the south. An upwelling Rossby wave favored the increase of SSS farther to the south. During the positive IOD events in 2011 and 2012, the above-mentioned processes reversed, although the decrease of SSS was weaker in magnitude.

scholarly journals Two Independent Triggers for the Indian Ocean Dipole/Zonal Mode in a Coupled GCM

2005 ◽  
Vol 18 (17) ◽  
pp. 3428-3449 ◽  
Author(s):  
Albert S. Fischer ◽  
Pascal Terray ◽  
Eric Guilyardi ◽  
Silvio Gualdi ◽  
Pascale Delecluse
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
Indian Ocean Dipole ◽  
El Nino ◽  
Tropical Indian Ocean ◽  
Sea Surface ◽  
Dynamical Response ◽  
Thermocline Depth ◽  
Second Phase ◽  
The Indian Ocean

Abstract The question of whether and how tropical Indian Ocean dipole or zonal mode (IOZM) interannual variability is independent of El Niño–Southern Oscillation (ENSO) variability in the Pacific is addressed in a comparison of twin 200-yr runs of a coupled climate model. The first is a reference simulation, and the second has ENSO-scale variability suppressed with a constraint on the tropical Pacific wind stress. The IOZM can exist in the model without ENSO, and the composite evolution of the main anomalies in the Indian Ocean in the two simulations is virtually identical. Its growth depends on a positive feedback between anomalous equatorial easterly winds, upwelling equatorial and coastal Kelvin waves reducing the thermocline depth and sea surface temperature off the coast of Sumatra, and the atmospheric dynamical response to the subsequently reduced convection. Two IOZM triggers in the boreal spring are found. The first is an anomalous Hadley circulation over the eastern tropical Indian Ocean and Maritime Continent, with an early northward penetration of the Southern Hemisphere southeasterly trades. This situation grows out of cooler sea surface temperatures in the southeastern tropical Indian Ocean left behind by a reinforcement of the late austral summer winds. The second trigger is a consequence of a zonal shift in the center of convection associated with a developing El Niño, a Walker cell anomaly. The first trigger is the only one present in the constrained simulation and is similar to the evolution of anomalies in 1994, when the IOZM occurred in the absence of a Pacific El Niño state. The presence of these two triggers—the first independent of ENSO and the second phase locking the IOZM to El Niño—allows an understanding of both the existence of IOZM events when Pacific conditions are neutral and the significant correlation between the IOZM and El Niño.

Assessing Sea Surface Salinity Derived by Aquarius in the Indian Ocean

2014 ◽  
Vol 11 (4) ◽  
pp. 719-722 ◽  
Author(s):  
Smitha Ratheesh ◽  
Rashmi Sharma ◽  
Rajesh Sikhakolli ◽  
Raj Kumar ◽  
Sujit Basu
Keyword(s):  
Indian Ocean ◽  
Sea Surface ◽  
Sea Surface Salinity ◽  
Surface Salinity ◽  
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 Impact of the Madden–Julian Oscillation on Summer Rainfall in Southeast China

2009 ◽  
Vol 22 (2) ◽  
pp. 201-216 ◽  
Author(s):  
Lina Zhang ◽  
Bizheng Wang ◽  
Qingcun Zeng
Keyword(s):  
Indian Ocean ◽  
Tropical Indian Ocean ◽  
Summer Rainfall ◽  
Western Pacific ◽  
Madden Julian Oscillation ◽  
Energy Propagation ◽  
Southeast China ◽  
The Indian Ocean ◽  
The Impact ◽  
The Western Pacific

Abstract The impact of the Madden–Julian oscillation (MJO) on summer rainfall in Southeast China is investigated using the Real-time Multivariate MJO (RMM) index and the observational rainfall data. A marked transition of rainfall patterns from being enhanced to being suppressed is found in Southeast China (east of 105°E and south of 35°N) on intraseasonal time scales as the MJO convective center moves from the Indian Ocean to the western Pacific Ocean. The maximum positive and negative anomalies of regional mean rainfall are in excess of 10% relative to the climatological regional mean. Such different rainfall regimes are associated with the corresponding changes in physical fields such as the western Pacific subtropical high (WPSH), moisture, and vertical motions. When the MJO is mainly over the Indian Ocean, the WPSH shifts farther westward, and the moisture and upward motions in Southeast China are increased. In contrast, when the MJO enters the western Pacific, the WPSH retreats eastward, and the moisture and upward motions in Southeast China are decreased. It is suggested that the MJO may influence summer rainfall in Southeast China through remote and local dynamical mechanisms, which correspond to the rainfall enhancement and suppression, respectively. The remote role is the energy propagation of the Rossby wave forced by the MJO-related heating over the Indian Ocean through the low-level westerly waveguide from the tropical Indian Ocean to Southeast China. The local role is the northward shift of the upward branch of the anomalous meridional circulation when the MJO is over the western Pacific, which causes eastward retreat of the WPSH and suppressed moisture transport toward Southeast China.

Meridional Distribution of Surface CO2 along 67°E of the Indian Ocean

2020 ◽  
Author(s):  
Dong-Jin Kang ◽  
Sang-Hwa Choi ◽  
Daeyeon Kim ◽  
Gyeong-Mok Lee
Keyword(s):  
Indian Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Sea Surface ◽  
Sea Surface Salinity ◽  
Surface Seawater ◽  
Surface Salinity ◽  
The North ◽  
The Indian Ocean ◽  
North And South

<p>Surface seawater carbon dioxide was observed from 3 °S to 27 °S along 67 °E of the Indian Ocean in April 2018 and 2019. Partial pressure of CO<sub>2</sub>(pCO<sub>2</sub>) in the surface seawater and the atmosphere were observed every two minutes using an underway CO2 measurement system (General Oceanics Model 8050) installed on R/V Isabu. Surface water temperature and salinity were measured as well. The pCO<sub>2</sub> was measured using Li-7000 NDIR. Standard gases were measured every 8 hours in five classes with concentrations of 0 µatm, 202 µatm, 350 µatm, 447 µatm, and 359.87 µatm. The fCO<sub>2</sub> of atmosphere remained nearly constant at 387 ± 2 µatm, but the surface seawater fCO<sub>2</sub> peaked at about 3 °S and tended to decrease toward the north and south. The distribution of fCO<sub>2</sub> in surface seawater according to latitude tends to be very similar to that of sea surface temperature. In order to investigate the factors that control the distribution of fCO<sub>2</sub> in surface seawater, we analyzed the sea surface temperature, sea surface salinity, and other factors. The effects of salinity are insignificant, and the surface fCO<sub>2</sub> distribution is mainly controlled by sea surface temperature and other factors that can be represented mainly by biological activity and mixing.</p>

A sea surface salinity dipole mode in the tropical Indian Ocean

2016 ◽  
Vol 47 (7-8) ◽  
pp. 2573-2585 ◽  
Author(s):  
Yuhong Zhang ◽  
Yan Du ◽  
Tangdong Qu
Keyword(s):  
Indian Ocean ◽  
Tropical Indian Ocean ◽  
Sea Surface ◽  
Sea Surface Salinity ◽  
Dipole Mode ◽  
Surface Salinity
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