# Features and trends of marine heat waves and marine cold spells along the Western Iberian Coast from four decades of satellite data

## TL;DR

This study compares marine heat waves and cold spells along the Western Iberian Coast using satellite data from 1982 to 2022.

## Contribution

It provides the first detailed comparison of marine heat waves and cold spells in the region, highlighting their spatial patterns and trends.

## Key findings

- The Western Iberian Coast experienced more marine cold spells than heat waves, with lower intensities.
- Coastal regions between Minho and Douro Estuaries showed favorable conditions for marine cold spells.
- Near the coastline, marine cold spells increased by 0.06 events per year.

## Abstract

Marine Heat Waves (MHWs) have been the focus of numerous studies due to the dramatic consequences they can have on coastal systems. However, Marine Cold Spells (MCSs) can also have harmful effects on the environment while play an important role in the context of global warming. Yet, there is lack of information on the physical attributes and long-term changes of MCSs. This study aims to investigate and compare the features and patterns of both MHWs and MCSs along the Western Iberian Coast (WIC) and its estuaries using satellite-derived Sea Surface Temperatures between 1982 and 2022. Overall, the WIC registered more MCSs than MHWs, although with lower intensities. The coastal region between Minho and Douro Estuaries and Cape São Vicente were favorable for MCSs development. The coastal regions of Minho through Aveiro and the south coast of Portugal registered MCSs and MHWs with the highest average and maximum intensities. No significant trends were observed for MHWs and MCSs features throughout the WIC. MHWs (MCSs) events were found to have been increasing (decreasing) offshore. However, an increase was registered near the coastline for MCS (0.06 events/year). Increased seasonal upwelling could be contributing to mask the development of MHWs and enhance MCSs.

The online version contains supplementary material available at 10.1038/s41598-025-31504-1.