Global Marine Heatwaves and Cold‐Spells in Present Climate to Future Projections. Issue 11 (28th October 2022)

• Record Type: Journal Article
• Authors: Yao, Yulong; Wang, Chunzai; Fu, Yao
• Is Part Of: Earth's future. Volume 10:Issue 11(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-10-28
• Subjects: Environmental sciences -- Periodicals; Environmental sciences; Periodicals; 550
• DOI: 10.1029/2022EF002787
• Languages: English
• ISSNs: 2328-4277

Abstract

Abstract: Marine heatwave (MHW) characteristics, such as total days, average duration, and mean intensity, have increased in most global oceans. In contrast, marine cold‐spell (MCS) characteristics have a decreasing trend over most regions. However, the difference between MHW and MCS in the mean and trend in the present and future climate is unclear. Here, we provide a comparative global assessment of these changes based on satellite sea surface temperature for 1982–2020 and climate model projections for 2021–2070. Globally, there are clear differences in the mean and trend between MHW and MCS metrics. On seasonal timescales, MHWs mainly occur in summer and autumn, while MCSs generally occur in winter and spring. The occurrence area of MHWs shows an increasing trend during 1982–2020, while the occurrence area of MCSs shows an opposite trend. Furthermore, the increasing trend in MHW average duration led to a near‐permanent MHW status in the future projections. Upper‐ocean warming due to anthropogenic forcing is closely related to increase in MHWs and decrease in MCSs. In addition, the shallower ocean mixed layer depth in the future is favorable for the occurrence of MHWs. In contrast, the projected weakening of the Atlantic meridional overturning circulation facilitates the occurrence of MCSs in the subpolar North Atlantic. These results provide a global baseline for the difference and relationship between MHW and MCS under present climate and future projections. Plain Language Summary: Marine heatwaves (MHWs), known as prolonged extreme oceanic warm water events, are expected to become more frequent with climate change. In contrast, marine cold‐spells (MCSs), known as extremely cold sea water events, have received less comprehensive and global attention despite their severe and long‐lasting impacts on marine ecosystems and fisheries. We provide a global comparative assessment of MHW and MCS changes based on sea surface temperature observations, reanalysis products, and climate models over 1982–2020 and 2021–2070. Globally, MHW total days, average duration, and mean intensity increase in the present and future climate. In contrast, the MCS metrics are decreasing in the present climate. However, the projected total days and average duration of MCS increase in the subpolar North Atlantic. Upper‐ocean warming due to anthropogenic forcing drives the increase of MHWs and the decrease of MCSs. Decreased ocean mixed layer depth in the present and future climate is favorable for the occurrence of MHWs. In contrast, the projected weakening of the Atlantic meridional overturning circulation facilitates the occurrence of MCSs in the subpolar North Atlantic. This study can aid the fisheries and aquaculture industries in better understanding climate change risks under global warming by considering both MHWs and MCSs. Key Points: Marine cold‐spells decrease in their total days and average duration in most global oceans in the present and future climate The differences in mean and trend between marine‐cold spell and heatwave metrics can be explained by upper‐ocean warming Weakening of the Atlantic meridional overturning circulation increases the projected marine cold‐spell total days and duration in the subpolar North Atlantic