EGU25-2006, updated on 14 Mar 2025
https://doi.org/10.5194/egusphere-egu25-2006
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Synergistic Impacts of Climate Variabilities over the North Atlantic Ocean on Marine Heatwaves in the North Sea
Yuxin Lin1,2, Zhiqiang Liu2,3, and Wenyan Zhang1
Yuxin Lin et al.
  • 1Helmholtz-Zentrum Hereon, Coastal Systems - Analysis and Modeling, Geesthacht, Germany
  • 2Department of Ocean Science and Engineering, Southern University of Science and Technology, Shenzhen, China
  • 3Center for Complex Flows and Soft Matter Research, Southern University of Science and Technology, Shenzhen, China

The Marine heatwaves (MHWs), defined as anomalous warm seawater events disrupting marine ecosystems and commercial fisheries, have become increasingly prolonged, frequent, and intense. While these trends are partially attributed to global warming, climate variability also plays a crucial role. Using observational datasets, this study explores how large-scale climate variability over the North Atlantic Ocean strengthens MHW in the North Sea. After removing the effects of global warming, empirical orthogonal function analysis revealed that the mechanisms driving MHWs are seasonally and regionally different. In winter, the total intensity of MHW increases significantly only when the North Atlantic Oscillation (NAO) and East Atlantic Pattern (EAP) are both in their positive phases. This combination generates southwesterly wind anomalies over the English Channel, facilitating warm water transport into the southern North Sea. Simultaneously, over the northeastern North Sea, reduced geopotential height enhances precipitation, strengthening stratification and further intensifying MHWs there. When the NAO and EAP are in negative or opposing phases, easterly wind anomalies prevail, which do not contribute to strengthened MHW. In summer, the total intensity of MHW increased (decreased) during the positive (negative) phase of the Atlantic Multidecadal Oscillation (AMO). A negative AMO phase often coincides with a positive NAO phase. Their combined effects increase cloud cover over the northern North Sea, reducing net heat flux and weakening MHW. Conversely, when AMO transitions to a positive phase, it leads to a negative NAO phase after several years, weakening their connection with MHW intensification. These findings highlight the combined influence of climate variability on MHWs in marginal seas and offer insights for improving MHW predictions.

How to cite: Lin, Y., Liu, Z., and Zhang, W.: Synergistic Impacts of Climate Variabilities over the North Atlantic Ocean on Marine Heatwaves in the North Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2006, https://doi.org/10.5194/egusphere-egu25-2006, 2025.