Biparjoy: The Changing Character of the Arabian Sea and its Impact on Cyclones

Video Producer: Vishnu Gopinath

Video Editor: Mohd. Irshad Alam

Senior Editor: Shohini Bose

The extremely severe cyclonic storm "Biparjoy" is rapidly advancing towards the east-central Arabian Sea, posing a significant threat to the coastal regions of Saurashtra and Kutch. According to the Indian Meteorological Department (IMD) communique, it is projected to continue its northward trajectory, after which it will turn northeastward, making landfall between Mandvi (Gujarat) and Karachi (Pakistan) on 15 June. 

With maximum sustained wind speeds of 125-135 kmph, gusting up to 150 kmph, "Biparjoy" is leading to heavy rainfall in Gujarat's coastal districts. The intensity of rainfall is expected to increase, with the possibility of extremely heavy downpours in some areas.

Over the past four decades, the Arabian Sea, located in the north Indian Ocean, has experienced a significant transformation in its character. Historically, it was known to be relatively cooler than its counterpart, the Bay of Bengal. 

The question is, why is this happening?

The Changing Face of the Arabian Sea

The Arabian Sea is a region of the northeastern Indian Ocean bounded by the Arabian Peninsula to the west and the Indian subcontinent to the east. Over the years, the Arabian Sea has experienced changes that have impacted the formation and intensity of cyclones in the region. Key factors contributing to these changes include sea surface temperature, monsoon patterns, and atmospheric conditions. There are three major reasons. 

First, there is a rise in sea-surface temperature. Rising sea surface temperatures have been observed in the Arabian Sea, largely attributed to global warming. Warmer waters provide more energy to tropical cyclones, potentially leading to their intensification. Increased sea surface temperatures can result in greater evaporation rates, leading to higher humidity levels and increased moisture availability for cyclone development.

Second, there is a changing monsoon pattern. The monsoon season influences the Arabian Sea, which brings significant rainfall and winds to the region. Changes in Indian monsoon patterns have been documented, and science shows that there is an effect on the formation of cyclones. For example, the Indian monsoon plays a crucial role in determining the strength and frequency of cyclones in the Arabian Sea. Monsoon intensity and timing variation has also impacted the conditions necessary for cyclone formation.

The third issue relates to the present atmospheric Conditions: The atmospheric conditions, including wind patterns and vertical wind shear, play a crucial role in cyclone formation and intensity. Changes in atmospheric circulation patterns can affect the development and tracks of cyclones in the Arabian Sea. Factors such as wind shear, which refers to the variation in wind speed and direction with height, can either enhance or inhibit cyclone formation and intensification.

The impact of these changing characteristics on cyclones in the Arabian Sea has been significant. Warmer sea surface temperatures have provided more energy to cyclones, potentially leading to their intensification and increasing the likelihood of severe cyclones. Monsoon pattern changes have influenced cyclones' timing, frequency, and tracks. Alterations in atmospheric conditions have also affected the formation and intensification of cyclones.

However, it is important to note that studying the changing character of the Arabian Sea and its impact on cyclones is an ongoing scientific research area. Climate models and observations are continually used to understand and predict these changes more accurately. 

Ocean Warming and Climate Impacts

In 2019, IPCC published a special report on oceans and the cryosphere (SROCC) as part of its 6th Assessment Cycle. The report dived deep into the two inter-connected systems assessing the impact of global warming on– the oceans and the cryosphere, the frozen part of the world. 

The report has made significant observations assessing the scientific literature on the impacts of ocean warming on the lives and livelihoods of people worldwide, especially on the coastal communities in the global south. It noted that the warming of the ocean is leading to changes in the distribution and abundance of fish stocks, posing challenges for fisheries management. Climate impacts on fisheries resources are reducing the effectiveness of international and national ocean governance.

Coastal ecosystems, such as wetlands, salt marshes, and seagrass meadows, are under stress from ocean warming and sea-level rise, compounded by human activities. Coral reefs are experiencing bleaching events and degradation, while intertidal rocky shores have reduced biodiversity and abundance of calcified organisms. Estuaries are facing increased hypoxia and eutrophication due to warming and nutrient loads. 

Coastal ecosystems provide vital services, but their ability to adapt may be limited by human-induced habitat fragmentation. Eastern Boundary Upwelling Systems (EBUS) have shown intensification in wind strength, potentially affecting upwelling patterns, ocean acidification, and deoxygenation. Harmful algal blooms and pathogenic organisms have increased in coastal areas, impacting food provision, tourism, and human health. Climate-resilient coastal adaptation frameworks have been developed, but the success of their implementation is yet to be fully assessed.

Projections: Impacts of Climate Change on Oceans by 2100

The SROCC report also projected changes in the ocean state and its impacts on various aspects of marine ecosystems under different emissions scenarios by the end of the 21st century. The high emissions scenario (RCP8.5) is expected to result in significantly larger and more widespread effects than the low emissions scenario (RCP2.6). Key projections include warming, ocean acidification, reduced stability of calcite minerals, oxygen loss, decreased near-surface nutrients, reduced primary productivity, and decreased fish production. These changes pose risks to key ecosystems and services important for human well-being and sustainable development.

By 2100, under RCP2.6, the ocean is projected to warm 2 to 4 times as much as observed since 1970, while under RCP8.5, the warming is projected to be 5 to 7 times as much. The upper ocean will experience increased stratification, and coastal regions will likely undergo significant changes in tidal amplitudes influenced by human coastal adaptation measures and climate drivers.

Ocean acidification is expected to cause corrosive conditions in certain regions, and oxygen levels are projected to decline globally, with an associated expansion of oxygen minimum zones (OMZs). Additionally, reduced nutrient supply and changes in environmental factors will lead to a decline in net primary productivity and reduced organic carbon supply to deep-sea ecosystems.

All these will impact coastal communities worldwide. With a large coastline of 7500 KMs in India, a conservative estimate shows that around 28 million people are directly associated with fishing and allied services for their livelihood. They are being affected inversely by these changes that they have not contributed to. 

Rising Arabian Sea Temperatures Amplify Cyclone Risks

The warming of the Arabian Sea has raised concerns about its impact on cyclones and their potential for devastating landfall. Recent studies have revealed that the Arabian Sea has experienced a temperature increase of approximately 1.2°C since March, attributed to climate change. These warmer conditions create a favourable environment for cyclones' rapid intensification and prolonged duration.

The changing dynamics of the Arabian Sea, driven by rising ocean temperatures, have resulted in more frequent, intense, and longer-lasting cyclones in the region. Given the ongoing warming trend and the projected increase in cyclone activity, it is vital to closely monitor these developments and enhance our understanding of their impacts.

The urgent need to address this issue is underscored by the potential for widespread damage caused by cyclones in the Arabian Sea. Mitigating greenhouse gas emissions and implementing measures to adapt to and manage the profound changes brought by climate change in the coming century are crucial steps to tackle this growing threat. Improved monitoring systems and comprehensive research efforts will aid in developing effective strategies to protect vulnerable coastal areas and communities from the escalating risks associated with cyclones in the Arabian Sea.

(Anjal Prakash is a Clinical Associate Professor (Research) and Research Director- at the Bharti Institute of Public Policy at ISB. He was the Coordinating Lead Author of the IPCCs SROCC report. This is an opinion piece. The views expressed above are the author’s own. The Quint neither endorses nor is responsible for them.)