Indian National Centre for Ocean Information Services (INCOIS), under the Ministry of Earth Sciences (MoES), has discovered that the Southern Annular Mode (SAM), an important climate pattern, plays a pivotal role in shaping the sea conditions across the Indian Ocean.
Scientists, who have been studying the SAM climate pattern and trying to understand how it shapes the wave patterns over extended time frames, state that it could help the country in better coastal planning, resource management and also in disaster preparedness.
Their study’s findings can also contribute to advancing the accuracy of wave predictions and can help identifying fair weather windows, thus benefitting the fisherfolk community and blue economy stake holders such as shipping, maritime boards and oil industry for their multi-million dollars worth operations at sea.
INCOIS scientists said that it is important to study ocean surface waves as they play a crucial role in shaping the coastal processes, and influencing numerous aspects of society, including shoreline erosion, sediment transport, coastal engineering and recreational activities.
Positive and Negative SAM
The scientific team used the 40-year data (1979 to 2018) from the European Centre for Medium-Range Weather Forecast to analyse seven parameters such as wave height, wave period and wind speed for the study.
They found that during a positive SAM phase, a cyclic pattern of warm sea surface temperature anomalies was seen, and strong winds caused increased wave activity in Indian Ocean. They also found a new swell generation region along the east African coast, which caused an increase in wave height in the Arabian Sea.
On the other hand, during a negative SAM phase, the eastern tropical southern Indian Ocean becomes the main region for generating swells, resulting in reduced wave heights in the Arabian Sea.
“Generally, inland vessel operations and oil exploration activities have a blanket ban during the monsoon season. By predicting the SAM phases in Ocean forecasting System, we can identify ‘Fair Sea state windows’ in monsoons. These fair windows can be utilised by oil and shipping industries for their operations, thus making a huge impact in the blue economy activities in the Indian coast,” said INCOIS group director and co-author of the paper T. M. Balakrishnan Nair.
His collaborating scientific colleagues have been Meenakshi Sreejith, P. G. Remya, B. Praveen Kumar and CSIR-National Institute of Oceanography’s G. Srinivas. The paper titled ‘Impact of southern annular mode on the Indian Ocean surface waves’ was published last month in the ‘International Journal of Climatology’.
