Assessing post‐tsunami effects on ocean colour at eastern Indian Ocean using MODIS Aqua satellite

Abstract

The 2004 Indian Ocean tsunami had been reported to cause vast destruction on marine environment, but its effect on the primary production and upwelling event was unknown. Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua ocean colour imageries were used to assess the tsunami effects on the chlorophyll‐a (chl‐a) and turbidity variations. Chlorophyll‐a and normalized water leaving radiance at 551 nm (nLw 551) before and after the tsunami event were processed using SeaWiFS data analysis system (SeaDAS), and the variations were examined. Results showed a sudden increase of chl‐a and nLw 551 at the north‐western Sumatra and middle of Malacca Straits (MS) after the tsunami. At western Sumatra, high sedimentation caused by the backwash resulted in overestimation of the chl‐a values. However, the chl‐a in the upwelling area in the northern MS did not exhibit any significant changes. The chl‐a variation in the northern MS was found to be related to the monsoon wind with about one week time lag. At the seriously eroded coastline along western Sumatra, continuous sedimentation was observed. The sedimentation problem became more severe during higher rainfall periods in April 2005. We strongly suggest a long term monitoring of this sedimentation problem.

Acknowledgement

The data used in this study were acquired as part of NASA's Earth–Sun System Division and archived and distributed by the Goddard Earth Sciences (GES) Data and Information Services Center (DISC) Distributed Active Archive Center (DAAC). We would also like to thank Tomas Gonzales for his comments and suggestions in preparing this paper.