Similar to excessively hot weather over the land, ocean water temperatures can be extremely warm for an extended period of time. These events, similar to their terrestrial counterparts, are known as marine heatwaves, or MHWs. Abnormally high ocean temperatures have significant impacts on marine ecosystems, for example contributing to the collapse of the cod fishery in the Northwest Atlantic. Marine heatwaves have been increasing in duration and intensity at a global scale due to the anthropogenic warming of the climate. To develop practical predictions of these events, a better understanding of the processes responsible for the development of MHWs is necessary.
In a recently published study in Frontiers in Marine Science, authors Robert Schlegel, Eric Oliver, and Ke Chen investigated the atmospheric and oceanic drivers for the onset and decline of MHWs on the Northwest Atlantic continental shelf. The forcing variables that induce the ocean surface mixed-layer temperature changes include air-sea heat flux, ocean horizontal advection, and other additional physical processes. The authors constructed a time series of the forcing variables and SSTa (Sea Surface Temperature Anomalies) during the MHWs events of 1993-2018. They examined the relationships between air-sea heat flux and SSTa and found that latent heat flux is the most common driver of the onset of MHWs, coupled with the change of mixed layer depth. The oceanic processes are dominant in the decay of MHWs. Additional self-organizing map (SOM) analysis revealed three primary synoptic-scale patterns during MHWs (low-pressure cyclonic Autumn-Winter systems, high-pressure anti-cyclonic Spring-Summer blocking, and mild but long-lasting Summer blocking) and provided a strong starting point for future research on the relationships between atmospheric drivers of air-sea heat flux and the formation of MHWs.
Read the full paper here.
Funding for this project was provided in part by the NOAA Climate Program Office, MAPP program, and Climate Variability & Predictability (CVP) program.
The Modeling, Analysis, Predictions, and Projections (MAPP) Program is a competitive research program in NOAA Research’s Climate Program Office. MAPP’s mission is to enhance the Nation’s and NOAA’s capability to understand, predict, and project variability and long-term changes in Earth’s system and mitigate human and economic impacts. To achieve its mission, MAPP supports foundational research, transition of research to applications, and engagement across other parts of NOAA, among partner agencies, and with the external research community. MAPP plays a crucial role in enabling national preparedness for extreme events like drought and longer-term climate changes. For more information, please visit www.cpo.noaa.gov/MAPP.