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<p>Marine heatwaves (MHW) are increasingly recognized for their ecological and climatic impacts, yet their behavior in the Southern Ocean (SO)—a key component of the global climate system—remains understudied. This study investigates the spatial and temporal variability of SO MHW from 1982 to 2022, focusing on two regional hotspots: the Western Pacific (WP) and North Ross Sea (NRS), highlighting regional dynamics, variability, and the influence of large-scale climate modes. SO exhibited weaker long-term MHW trends compared to the global average, but a marked intensification (frequency + 0.36 events/decade, + 15&#xa0;days/decade) in the last decade signals a recent shift under warming conditions. Regionally, NRS experienced stronger austral summer MHW intensity, while WP showed more frequent but less intense events in austral winter, indicating seasonal responses. A strong correlation between SST variance and MHW frequency in WP (R ≈ 0.85–0.86), and moderate correlation in NRS (R ≈ 0.78), highlights the role of background variability. ENSO moderately influenced NRS MHW frequency and days, whereas WP showed weaker teleconnection signatures. The Southern-Annular Mode (SAM) negatively correlated with MHW intensity and duration in NRS, during austral autumn, through wind-driven processes, including enhanced westerlies and Ekman transport, promoting cold-water upwelling and mixing. These mechanisms reduce surface warming and stratification, suppressing MHW development. EOF PC1 reflects large-scale variability (e.g., ENSO), while PC2 isolates polar-amplified signals near hotspots. Such decomposition improves understanding of how SST anomalies and MHW extremes co-evolve under climate forcing. This study underscores the importance of large-scale climate modes and regional processes in shaping SO MHW characteristics.</p>

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Southern Ocean marine heatwaves: variability, hotspots and teleconnections

  • 期刊论文

  • 发表日期：

    2025年7月19日

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  • K. Gurumoorthi,
  • Alvarinho J. Luis

摘要

Marine heatwaves (MHW) are increasingly recognized for their ecological and climatic impacts, yet their behavior in the Southern Ocean (SO)—a key component of the global climate system—remains understudied. This study investigates the spatial and temporal variability of SO MHW from 1982 to 2022, focusing on two regional hotspots: the Western Pacific (WP) and North Ross Sea (NRS), highlighting regional dynamics, variability, and the influence of large-scale climate modes. SO exhibited weaker long-term MHW trends compared to the global average, but a marked intensification (frequency + 0.36 events/decade, + 15 days/decade) in the last decade signals a recent shift under warming conditions. Regionally, NRS experienced stronger austral summer MHW intensity, while WP showed more frequent but less intense events in austral winter, indicating seasonal responses. A strong correlation between SST variance and MHW frequency in WP (R ≈ 0.85–0.86), and moderate correlation in NRS (R ≈ 0.78), highlights the role of background variability. ENSO moderately influenced NRS MHW frequency and days, whereas WP showed weaker teleconnection signatures. The Southern-Annular Mode (SAM) negatively correlated with MHW intensity and duration in NRS, during austral autumn, through wind-driven processes, including enhanced westerlies and Ekman transport, promoting cold-water upwelling and mixing. These mechanisms reduce surface warming and stratification, suppressing MHW development. EOF PC1 reflects large-scale variability (e.g., ENSO), while PC2 isolates polar-amplified signals near hotspots. Such decomposition improves understanding of how SST anomalies and MHW extremes co-evolve under climate forcing. This study underscores the importance of large-scale climate modes and regional processes in shaping SO MHW characteristics.