Publications

Idris, MS; Siang, HL; Amin, RM; Sidik, MJ (2022). Two-decade dynamics of MODIS-derived Secchi depth in Peninsula Malaysia waters. JOURNAL OF MARINE SYSTEMS, 236, 103799.

Abstract
Secchi disk depth (Z(sd)) is an essential environmental factor for studying ecosystem dynamics and biogeochemical processes in aquatic environments. Monitoring the long-term changes in water transparency is critical to predict the cascading impacts of climate change on marine ecosystems. We investigated the seasonal and interannual dynamics of Z(sd) in the eastern coast of Peninsula Malaysia (ECPM) and the Straits of Malacca (SoM) using a 21-year time series of MODIS ocean color data. To enable the reliable assessment of Z(sd) and its long-term variability, the performance of existing and regional algorithms was investigated using in-situ optical measurements collected during different monsoon seasons and in various environmental conditions. Our validation results showed that the existing Z(sd) algorithms performed adequately, but exhibited large errors, especially at relatively high Z(sd) values. On the other hand, the regional empirical algorithm based on a direct relationship between remote sensing reflectance and Z(sd) showed significant improvements by reducing the overall bias observed in existing Z(sd) schemes. The results indicated that the monthly climatological Z(sd) over the period 2000-2020 showed distinct patterns in different seasons. The ECPM waters had deeper Z(sd) than SoM waters. Maximum transparency usually occurred during the southwest and spring inter-monsoon and minimum transparency occurred during the northeast monsoon. Long-term seasonal evolution of Z(sd) reveals that widespread and persistent anomalies dominated the ECPM and SoM regions. Interannual trends indicate notable and complex changes in Z(sd) that were probably driven by variability in the ocean-atmosphere dynamics of Nino-Southern Oscillation (ENSO) and local environmental conditions. This study highlights the extensive analysis of Z(sd) status and its spatio-temporal pattern from space, which can significantly benefit long-term ocean monitoring efforts in the ECPM and SoM regions.

DOI:
10.1016/j.jmarsys.2022.103799

ISSN:
1879-1573