Research Progresses in the Upwelling off the Southern Coast of Sri Lanka

Recently, Ocean Dynamics Laboratory of TIO published a paper “The strong upwelling event off the southern coast of Sri Lanka in 2013 and its relationship with Indian Ocean Dipole events” in the Journal of Climate (IF 5.7), with collaboration of State Key Laboratory of Marine Environmental Science of Xiamen University and Marine Science Department of Pathein University of Myanmar.

This research reveals that the upwelling area in 2013 was 5.7 times larger than that in a normal year, and lasts from June to August, with the peaks of the cooling anomaly reaching -1.5 °C and the positive chlorophyll-a concentration anomaly exceeding 3.1 mg m-3. In 2013, the strengthened southwest monsoon associated with the negative unseasonable Indian Ocean Dipole (nIODJJA) event impinges on the Sri Lankan landmass, resulting in a stronger westward alongshore wind stress and positive wind stress curl anomaly. It causes the stronger coastal upwelling that year.

Further analysis indicates that the interannual variability of the upwelling, as represented by a newly constructed index based on satellite observations, is primarily caused by the variations of local wind associated with the IOD. The upwelling off the southern coast of Sri Lanka weakens (strengthens) in the positive (negative) IOD years. However, an analysis based on 21 IOD events during 1982-2019 demonstrates that the effects of the three types of IOD events, including IODJJA, prolonged IOD (IODLONG) and normal IOD (IODSON), on the upwelling are different. Compared to the IODSON events, the IODJJA and IODLONG events tend to have stronger influences due to their earlier developing phases. 

Link to the paper:

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