Influence of ENSO and IOD Interaction on Sea Level Variability in Indonesia

Indonesia, located in the Indonesian Maritime Continent (IMC) region, is vulnerable to the impacts of global warming, which causes significant changes to atmospheric and oceanic conditions. Climate phenomena such as ENSO and IOD significantly influence weather variability in this region. This study aims to assess the relationship between sea level and ENSO and IOD events, as well as the distribution of sea level changes in Indonesia from 2009 to 2018. The data analyzed comprised oceanographic and atmospheric parameters, along with the SOI and DMI climate indices. Results show that the negative La Niña-IOD phase (2010–2011) increased sea level (> 1.05 m) and rainfall (> 300 mm/month) due to warm water masses (26°C) accumulating in western and central waters, supported by easterly winds (> 6 m/s) and lower surface pressure (< 1012 hPa). Conversely, the strong El Niño-Positive IOD phase (2015–2016) lowered sea level (< 0.90 m), reduced rainfall (< 50 mm), increased surface pressure (1012–1016 hPa), and strengthened dry southeast winds (8–12 m/s), causing water mass shifts to the Indian Ocean and eastern Pacific. The correlation between sea level and SOI was positive (r = 0.606; R² = 0.367; p < 0.01), while that with DMI was negative (r = -0.305; R² = 0.093; p < 0.01). Additionally, cross-correlation analysis indicates that sea level changes occur gradually over 7 to 27 days through the cross-Indonesian current.