Comparing Global Marine Cold Spells (MCS) and Marine Heatwaves (MHW)

• Main Authors: Peal, Robert, Worsfold, Mark
• Format: Conference Object
• Language: unknown
• Published: 2022
• Subjects: Southern Ocean
• Online Access: https://zenodo.org/record/6840556; https://doi.org/10.5281/zenodo.6840556

Presented at the GHRSST XXIII international science team meeting, 27 June-1 Jyuy 2022, online and in-person (Barcelona). #GHRSST23 Short abstract Global warming is causing extreme climate events to become more frequent and more severe. Marine Heat Waves (MHW) and Marine Cold Spells (MCS) are prolonged, discrete periods of anomalously high/low SSTs with wide ranging impacts from dramatic shifts in biodiversity to changes in fishery yields. Previous research has found that MHW are increasing in frequency and intensity but MCS remain less well understood. We compared the global MCS and MHW intensities and trends in their frequency over the period 1982-2020. These events were also assigned a category from 1 (moderate) to 4 (extreme). Our findings show that in much of the ocean, MCS have become less frequent by around one event every five years while MHW have become more frequent by around one event every five to ten years. Most of these changes are due to increases in category I and II MHW, and decreases in category I and II MCS. However, events in parts of the Southern Ocean go against these trends with MHW becoming slightly less frequent and MCS becoming more frequent. Category III and IV MHW remain less common than the milder events, and at individual locations they are occurring at a roughly constant rate. However, these events are becoming more widespread. Category III and IV MCS are rare but are continuing to occur at a near constant rate in much of the ocean.