Abstract

Using observations and long term simulations of an ocean-biogeochemical coupled model, we investigate the biological response in the southern subtropical Indian Ocean (SIO) associated with Ningaloo Niño and Niña events. Ningaloo events have large impact on sea surface temperature (SST) with positive SST anomalies (SSTA) seen off the west coast of Australia in southern SIO during Ningaloo Niño and negative anomalies during Niña events. Our results indicate that during the developing period of Ningaloo Niño, low chlorophyll anomaly appears near the southwest Australian coast concurrently with high SSTA and vice-versa during Niña, which alter the seasonal cycle of biological productivity. The difference in the spatiotemporal response of chlorophyll is due to the southward advection of Leeuwin current during these events. Increased frequency of Ningaloo Niño events associated with cold phase of Pacific Decadal Oscillation (PDO) resulted in anomalous decrease in productivity during Austral summer in the SIO in the recent decades.

Highlights

  • Changes in biological productivity have impact on the world climate

  • We explore the potential role of Ningaloo Niño/Ningaloo Niña in modulating the biological productivity off the coast of Australia in the southern subtropical Indian Ocean (SIO)

  • The Ningaloo Niño/Niña plays a key role in influencing the strength of LC, affecting the variability of chlorophyll close to the Australian coast, influencing the local ecosystem

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Summary

Introduction

Changes in biological productivity have impact on the world climate. The subtropical southern ocean region is low in biological productivity, owing to the lack of supply of nutrients to surface layer. Another important driver of LC variability is the Ningaloo events, a climate phenomenon associated with positive sea surface temperature (SST) anomalies off the west coast of Australia[16,17,18] during Niño and negative anomalies during Niña.

Results
Conclusion

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