Investigating the Response of Temperature and Salinity in the Agulhas Current Region to ENSO Events

Corinne B. Trott,Caroline E. Washburn,Bulusu Subrahmanyam

doi:10.3390/rs13091829

Corinne B. Trott, Caroline E. Washburn + Show 1 more

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https://doi.org/10.3390/rs13091829

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Abstract

The Agulhas Current is a critical component of global ocean circulation and has been observed to respond to El Niño Southern Oscillation (ENSO) events via its temperature and salinity signatures. In this research, we use sea surface salinity (SSS) from the National Aeronautics and Space Administration’s (NASA) Soil Moisture Active Passive (SMAP) satellite, sea surface temperature (SST) observations from the Canadian Meteorological Centre (CMC), sea surface height (SSH) anomalies from altimetry, and the Oceanic Niño Index to study the SMAP satellite time period of April 2015 through March 2020 (to observe full years of study). We see warming and high salinities after El Niño, cooling and fresher surface waters after La Niña, and a stronger temperature response than that of salinity. About one year after the 2015 El Niño, there is a warming of the entire region except at the Antarctic Circumpolar Current. About two years after the event, there is an increase in salinity along the eastern coast of Africa and in the Agulhas Current region. About two years after the 2016 and 2018 La Niñas, there is a cooling south of Madagascar and in the Agulhas Current. There are no major changes in salinity seen in the Agulhas Current, but there is a highly saline mass of water west of the Indonesian Throughflow about two years after the La Niña events. Wavelet coherence analysis finds that SSS and ENSO are most strongly correlated a year after the 2015 El Niño and two years after the 2016 La Niña.

Highlights

The variability of currents that are a part of the global conveyor belt, such as the Agulhas Current, can have major impacts on global climate
To observe the full pathways of El Niño Southern Oscillation (ENSO) signals across the Indian Ocean during the Soil Moisture Active Passive (SMAP) time period, the area of study chosen is 0◦ –120◦ E and 5◦ S–55◦ S, which covers the full southern Indian Ocean as well as the full Agulhas Leakage and Agulhas Retroflection regions
We studied the effects of ENSO events on sea surface temperature (SST) and sea surface salinity (SSS) in the Agulhas Current for the first time focusing on the SMAP satellite era

Summary

Introduction

The variability of currents that are a part of the global conveyor belt, such as the Agulhas Current, can have major impacts on global climate. The Agulhas Current is a western boundary current that flows off the eastern coast of South Africa. It originates south of the Mozambique Channel and flows towards the southern tip of Africa where it retroflects back into the Indian Ocean. The retroflection is between 16◦ E and 20◦ E with a loop diameter of 340 km and it sheds rings into the Atlantic that are about. The Agulhas Current does shed some of its water as rings, but most is retroflected along with water from the Southern Ocean [2].

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