Role of El Niño Southern Oscillation (ENSO) Events on Temperature and Salinity Variability in the Agulhas Leakage Region

Paris, Morgan L.; Subrahmanyam, Bulusu

doi:10.3390/rs10010127

Cited by 6 publications

(5 citation statements)

References 29 publications

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“…Our analysis of lagged correlations with the multivariate ENSO index reveals a 12-to 18-month lag of δ 18 O seawater and salinity at Ifaty and the AC region. These results agree with the 2-year lag found for the Agulhas leakage region, which is further downstream from our coral sites and implies a role for ENSO in interannual timescales of ocean connectivity (Potemra, 2001;Schouten et al, 2002;Wijffels and Meyers, 2004;de Ruijter et al, 2005;Palastanga et al, 2006;Putrahasan et al, 2016;Paris and Subrahmanyam, 2018). Salinity studies in the Agulhas leakage region have revealed a 20-to 26-month lag to ENSO forcing, whereby a fresh anomaly is replaced 2 years later by a saline anomaly following El Niño (and vice versa for La Niña) (Paris and Subrahmanyam, 2018;Trott et al, 2021).…”

Section: Large-scale Drivers Of Ac Core Region Sst and Salinitysupporting

confidence: 91%

“…On interannual timescales, the AC and AL region is apparently sensitive to the El Niño-Southern Oscillation (ENSO), with a 24-month lag (Putrasahan et al, 2016;Elipot and Beal, 2018;Paris and Subrahmanyam, 2018;Trott et al, 2021). Anomalous wind stress curl in the southern Indian Ocean in response to ENSO excites the westward propagating oceanic Rossby waves (Feng and Myers, 2003;Palastanga et al, 2006;Grunseich et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

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A 334-year coral record of surface temperature and salinity variability in the greater Agulhas Current region

Zinke

Watanabe²,

Rühs³

et al. 2022

Clim. Past

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Abstract. The Agulhas Current (AC) off the southern tip of Africa is one of the strongest western boundary currents and a crucial choke point of inter-ocean heat and salt exchange between the Indian Ocean and the southern Atlantic Ocean. However, large uncertainties remain concerning the sea surface temperature (SST) and salinity (SSS) variability in the AC region and their driving mechanisms over longer timescales, due to only short observational datasets being available and the highly dynamic nature of the region. Here, we present an annual coral skeletal Sr/Ca composite record paired with an established composite oxygen isotope record from Ifaty and Tulear reefs in southwestern Madagascar to obtain a 334-year (1661–1995) reconstruction of δ18Oseawater changes related to surface salinity variability in the wider Agulhas Current region. Our new annual δ18Oseawater composite record from Ifaty traces surface salinity of the southern Mozambique Channel and AC core region from the SODA reanalysis between 1958 and 1995. δ18Oseawater appears to be mainly driven by large-scale wind forcing in the southern Indian Ocean on interannual to decadal timescales. The δ18Oseawater and SST at Ifaty show characteristic interannual variability of between 2 and 4 years and interdecadal variability of 8 to 16 years, coherent with El Niño–Southern Oscillation (ENSO) records. Lagged correlations with the multivariate ENSO index reveals a 1–2-year lag of δ18Oseawater and salinity at Ifaty and the AC region, suggesting that propagation of anomalies by ocean Rossby waves may contribute to salinity changes in the wider southwestern Indian Ocean. The δ18Oseawater and SST reconstructions at Ifaty reveal the highest interannual variability during the Little Ice Age, especially around 1700 CE, which is in agreement with other Indo-Pacific coral studies. Our study demonstrates the huge potential to unlock past interannual and decadal changes in surface ocean hydrology and ocean transport dynamics from coral δ18Oseawater beyond the short instrumental record.

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Section: Large-scale Drivers Of Ac Core Region Sst and Salinitysupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

A 334-year coral record of surface temperature and salinity variability in the greater Agulhas Current region

Zinke

Watanabe²,

Rühs³

et al. 2022

Clim. Past

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“…SMAP is available from 2015 to present. Satellite-derived salinity has been used in several studies of the Indian Ocean but is underutilized in monsoon studies on the whole (Murty et al, 2004;Nyadjro et al, 2012;Nyadjro & Subrahmanyam, 2016;Paris & Subrahmanyam, 2018;Subrahmanyam et al, 2018).…”

Section: Data 211 Reanalysis Productsmentioning

confidence: 99%

The Role of Salinity in the Southeastern Arabian Sea in Determining Monsoon Onset and Strength

2020

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In this study, we examine the role of freshwater transported from the Bay of Bengal into the southeastern Arabian Sea (SEAS) in determining both the timing of monsoon onset and the strength of the ensuing monsoon. To do this, we use a combination of satellite-derived salinity data and reanalysis products from 1980 to 2016 in order to discuss seasonal, interannual, subdecadal, and long-term decadal variability in various atmospheric and oceanic contributors such as ocean heat content, freshwater transport, ERA5 instantaneous moisture flux, mixed layer depth, and barrier layer thickness. The salt budget in the SEAS reveals the dominance of meridional freshwater advective transport that brings in variability in salinity and thus in salinity stratification, as well as in mixed layer processes. We find that these parameters exhibit the prevalence of a long-term decadal variability (with trends of increasing/decreasing phases over a 15-year duration) over which interannual (3-year trend) and intradecadal (7-year trend) variability trends are superimposed. The patterns of both the 3-and 7-year trends follow each other closely, and relatively high amplitudes are seen in the 3-year trends. The long-term decrease in moisture flux and freshwater transport into the SEAS along with a rise in ocean heat content over a 15-year duration after 1994 contributed to a lack of strong monsoons in recent years; the prevailing interannual and intradecadal variability in these parameters associated with the Indian Ocean Dipole and El Niño Southern Oscillation events favored weaker and normal monsoons after 1994. Plain Language SummaryThe timing and intensity of the southwest monsoon is difficult to forecast and has been the subject of a great deal of research. In particular, the genesis of a monsoon onset vortex over the southeastern Arabian Sea (SEAS) encompassing the Arabian Sea Mini Warm Pool has received increased attention for the role it plays on the onset of the southwest monsoon. In our study, we examine how the low salinity waters transported from the Bay of Bengal (both along the east coast of India and from the southern Bay of Bengal) into the SEAS region influence the strength and timing of the ensuing southwest monsoon. Our finding is that this low salinity water has a significant impact on barrier layer formation in the SEAS and the vertical thermal structure of the Arabian Sea Mini Warm Pool. Further examination of subdecadal, decadal, and long-period decadal trends from 1980 to 2016 shows that instantaneous moisture fluxes and zonal winds over the SEAS have decreased substantially, and barrier layer thickness has increased since 1994 in association with the increasing trend in ocean heat content and contributed to the lack of strong southwest monsoons after 1994.

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“…Various studies of the linkage of the warm pool with large scale atmospheric circulation and oceanic processes have been launched [24][25][26][27]. The upper-layer volume fluctuations of the WPWP were found closely related to the oceanic circulation driven by the trade wind, and during El Niño events, the eastern sector volume increased yet the western sector decreased in much less magnitude [20].…”

Section: Introductionmentioning

confidence: 99%

Seasonal and Interannual Variability of the Indo-Pacific Warm Pool and its Associated Climate Factors Based on Remote Sensing

et al. 2020

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With satellite observed Sea Surface Temperature (SST) accumulated for multiple decades, multi-time scale variabilities of the Indo-Pacific Warm Pool are examined and contrasted in this study by separating it into the Indian Ocean sector and the Pacific Ocean sector. Surface size, zonal center, meridional center, maximum SST and mean SST as the practical warm pool properties are chosen to investigate the warm pool variations for the period 1982–2018. On the seasonal time scale, the oscillation of the Indian Warm Pool is found much more vigorous than the Pacific Warm Pool on size and intensity, yet the interannual variabilities of the Indian Warm Pool and the Pacific Warm Pool are comparable. The Indian Warm Pool has weak interannual variations (3–5 years) and the Pacific Warm Pool has mighty interdecadal variations. The size, zonal movement and mean SST of the Indian Ocean Warm Pool (IW) are more accurate to depict the seasonal variability, and for the Pacific Ocean Warm Pool (PW), the size, zonal and meridional movements and maximum SST are more suitable. On the interannual scale, except for the meridional movements, all the other properties of the same basin have similar interannual variation signals. Following the correlation analysis, it turns out that the Indian Ocean basin-wide index (IOBW) is the most important contributor to the variabilities of both sectors. Lead-lag correlation results show that variation of the Pacific Ocean Warm Pool leads the IOBW and variation of the Indian Ocean Warm Pool is synchronous with the IOBW. This indicates that both sectors of the Indo-Pacific Warm Pool are significantly correlated with basin-wide warming or cooling.

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Role of El Niño Southern Oscillation (ENSO) Events on Temperature and Salinity Variability in the Agulhas Leakage Region

Abstract: This study explores the relationship between the Agulhas Current system and El

Cited by 6 publications

References 29 publications

A 334-year coral record of surface temperature and salinity variability in the greater Agulhas Current region

A 334-year coral record of surface temperature and salinity variability in the greater Agulhas Current region

The Role of Salinity in the Southeastern Arabian Sea in Determining Monsoon Onset and Strength

Seasonal and Interannual Variability of the Indo-Pacific Warm Pool and its Associated Climate Factors Based on Remote Sensing

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