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| Abstract Submission No. | ABS-2022-05-0200 |
| Title of Abstract | Observed variability of monsoon blooms in the north-central Arabian Sea and its implication to deeper water oxygen concentration: A Bio-Argo study |
| Authors | Teesha Mathew*, Satya Prakash, Lakshmi R Shenoy, Abhisek Chatterjee |
| Organisation | INCOIS |
| Address | INCOIS,Ocean Valley, near Aleap, PragathiNagar, Nizampet Hyderabad, Telangana, India Pincode: 500090 Mobile: 7842202060 E-mail: tshaocean@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | The central Arabian Sea (CAS), the second most intense Oxygen Minimum Zones (OMZs) in the world oceans, is productive during both the summer and winter monsoons. In this present study, we analysed five years (2013-2017) record of chlorophyll and dissolved oxygen concentration from a Bio-Argo float in the CAS. Though the surface bloom was observed during both the monsoons and sub-surface chlorophyll was also persistently observed, the intensity and duration of the bloom has been decreasing over the past few years. Also, the winter bloom was more prominent compared to the summer bloom in the study region which is located north of CAS. Our analysis shows that the observed inter-annual variability in the summer bloom can be attributed to the variabilities in wind speed, oceanic near surface stratification and advection of nutrient rich water from the western Arabian Sea. During the winter monsoon, the upwelling Rossby wave propagating from the west coast of India also influences productivity as far as north of 15ºN. We also observed that the dissolved oxygen concentration in the deeper waters has been increasing during the past few years and it is consistent with the decrease in the surface chlorophyll. We speculate that the decrease in surface productivity has reduced the oxygen demand in the deeper layer and hence is the observed marginal increase in the deeper layer dissolved oxygen concentration. This is in contrast with the reports based on observation and model that suggest a decline in the oxygen inventory of the ocean. Also, in the event of recent reports on decreasing trend in productivity in the Arabian Sea, the present study provides new insights on the possible effect of declining productivity on the dissolved oxygen concentration under the climate change regime. |