Analysis of Long-term Trends and Variability of Sea Surface Chlorophyll-a and Temperature in The Northern Papua Sea, Indonesia

Muhammad Ridwan Ramadhan 

Chlorophyll-a serves as an important proxy for marine ecological productivity, and its dynamics playing pivotal role in the marine productivity, especially within the coral biodiversity hotspot such as Coral Triangle’s Northern Papua Sea (NPS). Consequently, elucidating the dynamics in such region is essential. This work aims to investigate the long-term trends and variability of the sea surface chlorophyll-a (SSC). Concurrently, sea surface temperature (SST) was also analyzed to quantify its influence on, and relationship with, observed SSC pattern. Employing over two decades (1998-2023) of satellite observations sourced by Copernicus Marine Service (CMS), advanced statistical techniques were used, including Mann-Kendall (MK) test, continuous wavelet transforms (CWT), cross wavelet transforms (XWT) to investigate the dominant modes of both parameters. The results of this study show a negative correlation between SST and SSC (r=-0.22), in addition, the highest lag correlation results were obtained for 2 months with a correlation value of 0.31. SST variability shows significant periodicity in the semi-annual period (~4-8 months). On the other hand, SSC displays a very different pattern, where significant periodicity variability is produced on an intraseasonal to semi-annual scale (~0-16 months) and a strong interannual signal (~12-16 months). The findings in this study indicate the sensitivity of the Northern Papua Sea to thermal variability caused by the ENSO forcing and indicate the need for further research on chlorophyll-a dynamics equipped with in-situ data, as well as vertical chlorophyll-a analysis to better understand its dynamics.