Preprints
https://doi.org/10.5194/os-2021-52
https://doi.org/10.5194/os-2021-52

  11 Jun 2021

11 Jun 2021

Review status: this preprint is currently under review for the journal OS.

Marine Heatwaves in the Arabian Sea

Abhisek Chatterjee1, Gouri Anil2, and Lakshmi R. Shenoy1,3 Abhisek Chatterjee et al.
  • 1Indian National Centre for Ocean Information Services, Ministry of Earth Sciences, Hyderabad, India
  • 2Cochin University of Science and Technology, Cochin, India
  • 3Kerala University of Fisheries and Ocean Studies, Cochin, India

Abstract. Marine heatwaves (MHWs) are prolonged warm sea condition events that cause a destructive impact on marine ecosystems. The documentation of MHWs and assessment of their impacts are largely confined to a few regional seas or in global mean studies. The Indian Ocean received almost no attention in this regard despite the fact that this ocean basin, particularly the Arabian Sea, is warming at the most rapid pace among the other tropical basins in recent decades. This study shows the characteristics MHWs for the Arabian Sea during 1982–2019. Our analysis shows that the duration of MHWs exhibit a rapidly increasing trend of ~20 days/decade (1.5–2 count/decade) in the northern Arabian Sea and in the southeastern Arabian Sea close to the west coast of India; which is more than 15 fold increase in the MHW days from the early 80s'. At the same time increase in MHW frequency is ~1.5–2 count/decade i.e an increase of ~6 fold, indicating more frequent and much longer heatwave events in the recent decade. Notably, since the beginning of the satellite record, the year 2010 and 2016 saw the maximum number of heatwave days with more than 75 % of days of the pre-monsoon and summer monsoon season experienced heatwaves. The accelerated trend of the heatwave days is found to be driven by the rapid rise of the mean SST of the Arabian Sea in the recent decade. Moreover, longer heatwave days are also associated with the dominant climate modes and among them, Indian Ocean Basin mode via the decaying phase of the El-Niño is found to be the most influencing mode contributing in more than 70–80 % of observed heatwave days in this basin. Mixed layer heat budget analysis suggests significant heterogeneity in the dominant processes across the years; however, weakening of latent heat loss is in general one of the key mechanism in the genesis of most of the MHWs.

Abhisek Chatterjee et al.

Status: open (until 07 Oct 2021)

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Abhisek Chatterjee et al.

Abhisek Chatterjee et al.

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Short summary
Marine heatwave refers to discrete, prolonged warm ocean condition known to cause severe destruction in marine ecosystems. We find that coastal waters off the west coast of India have experienced a rapid 15-fold increase in heatwave days since the early 80s'. This resulted in more frequent and longer marine heatwave events in the last decade. we show that the rapid warming in the Arabian Sea in the last decade is the primary cause of the observed enhanced heatwave events in this basin.