Inshore Ecological Impact Studies Of The Physical Processes In The Andaman Sea

Andaman Sea is significantly affected by the Asian monsoon system. While, theinfluence from ocean processes driven by the monsoon system to the local marineecosystem is still an open question. This article tries to answer above questions. Thecurrent work mainly includes two aspects. First is the impact, from the seasonal tointerannual thermocline variations in Andaman Sea, on the marine ecosystem alongthe eastern coastal area. The other part is the effect from the monsoon driven oceanwaves on the coral reef in the eastern and western coast of islands.Andaman Sea is located at the northeast of India Ocean. It has been separatedfrom Bay of Bengal by Andaman Islands and Nicobar Islands. The unique topographydistribution is benefit to the generation of the internal wave in the eastern part ofAndaman Sea. Considering the impact from the abundant monsoon precipitation andland runoff, the upper ocean salinity is lower than the subsurface, which is help toform the stable stratification, which leads to the oxygen minimum zones (OMZ) in thesubsurface of Andaman Sea. OMZ in Andaman Sea is located at the level lower thanthe permanent thermocline (approximately100-130m depth).With the combination ofterrain distribution, the thermocline and OMZ, the eastward propagating internal wavetriggered over the region adjacent to Andaman Islands and Nicobar Islands is able tobring hypoxia water from the deep ocean to the east shore, which always bringecological disaster to the local area. For example, in the spring of1995,1998and2007, we identified a wide range death of marine organism in the eastern coast ofAndaman Sea. Based on the analysis for kind of oceanic variable as well theatmospheric ones, we also found the above phenomena is related with tropical IndiaOcean Dipole mode and El Nino events During these period, anomalous easterly windcontrolled the equatorial Indian Ocean, which trigged the equatorial Kelvin wave tomove eastward. As the forcing Kelvin wave reach the eastern coast region, the wavesreflected northward and propagated into the eastern coast of Andaman Sea, whichmake the thermocline being shallower (<100m).The above process is helpful for the large amplitude internal waves to bring the hypoxia water entering the coastal region,which cause the marine ecosystem disaster.Lots of ocean observations confirmed that the distribution and structure of thecoral reef in the east and west coast of islands is asymmetric in Andaman Sea. Withthe analysis of ocean wave datasets from the satellite altimeter, we found the possiblereason responsible for such asymmetry. The distinct distribution of the ocean wavesheight affected by the monsoon circulation play great role on both sides of islands,which apparently affect the coral reef at location. MASNUM wave model has beenperformed to confirm such hypothesis.