<p>Marine heatwaves (MHWs) and cold spells (MCSs) are prolonged periods of extreme ocean temperature anomalies that significantly impact aquatic ecosystems and oceanic processes. Mesoscale eddies, characterized by anticyclonic eddies (AEs) and cyclonic eddies (CEs) circulations and identified using a scale-selective eddy identification algorithm, play a pivotal role in modulating ocean temperature dynamics by redistributing and storing heat. This study examines the influence of AE and CE on the frequency and intensity of MHW and MCS in a tropical region, specifically focusing on the Natuna Sea, Indonesia, over 30 years (1993–2022). Our analysis reveals an increasing trend in MHW frequency at a rate of 1.74 ± 0.53 events/decade, while MCS exhibits a decreasing trend of -2.10 ± 1.23 events/decade. The most pronounced MHW events occurred during the warmest years of the study period, notably in 1998 (6.96 events/year), 2010 (5.56 events/year), and 2014 (7.53 events/year). Mesoscale eddies were identified using sea level anomaly data, with absolute dynamic topography corrections applied to improve detection in coastal areas. Eddy sizes were predominantly ~50 km in coastal regions and ~100 km in offshore areas. Within the Indonesian Exclusive Economic Zone (EEZ), 248 AE and 243 CE were detected, of which 191 (77%) and 182 (75%) were associated with MHW and MCS occurrences, respectively. The proximity of MHW/MCS events to the eddy centers was typically less than 0.11° (~12 km). The mixed layer depth (MLD) alterations induced by these eddies significantly influenced temperature variations (<InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10236_2025_1673_Article_IEq1.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="92" /> </InlineMediaObject> <EquationSource Format="TEX">$\Delta T < 0.2^\circ C$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Δ</mi> <mi>T</mi> <mo><</mo> <mn>0</mn> <mo>.</mo> <msup> <mn>2</mn> <mo>∘</mo> </msup> <mi>C</mi> </mrow> </math></EquationSource> </InlineEquation>), with vertical impacts extending to depths of 10–20 m during both MHW and MCS events. These findings offer valuable insights into regional climate variability and its potential implications for marine ecosystems.</p>

Eddy-induced modulation of marine heatwaves and cold spells in a tropical region: a case study in the natuna sea area

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发表日期：

2025年3月11日

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Gandhi Napitupulu

摘要

Marine heatwaves (MHWs) and cold spells (MCSs) are prolonged periods of extreme ocean temperature anomalies that significantly impact aquatic ecosystems and oceanic processes. Mesoscale eddies, characterized by anticyclonic eddies (AEs) and cyclonic eddies (CEs) circulations and identified using a scale-selective eddy identification algorithm, play a pivotal role in modulating ocean temperature dynamics by redistributing and storing heat. This study examines the influence of AE and CE on the frequency and intensity of MHW and MCS in a tropical region, specifically focusing on the Natuna Sea, Indonesia, over 30 years (1993–2022). Our analysis reveals an increasing trend in MHW frequency at a rate of 1.74 ± 0.53 events/decade, while MCS exhibits a decreasing trend of -2.10 ± 1.23 events/decade. The most pronounced MHW events occurred during the warmest years of the study period, notably in 1998 (6.96 events/year), 2010 (5.56 events/year), and 2014 (7.53 events/year). Mesoscale eddies were identified using sea level anomaly data, with absolute dynamic topography corrections applied to improve detection in coastal areas. Eddy sizes were predominantly ~50 km in coastal regions and ~100 km in offshore areas. Within the Indonesian Exclusive Economic Zone (EEZ), 248 AE and 243 CE were detected, of which 191 (77%) and 182 (75%) were associated with MHW and MCS occurrences, respectively. The proximity of MHW/MCS events to the eddy centers was typically less than 0.11° (~12 km). The mixed layer depth (MLD) alterations induced by these eddies significantly influenced temperature variations ( $\Delta T < 0.2^\circ C$ $Δ T < 0 . 2^{\circ} C$ ), with vertical impacts extending to depths of 10–20 m during both MHW and MCS events. These findings offer valuable insights into regional climate variability and its potential implications for marine ecosystems.