Marine heatwaves in the Humboldt current system: from 5-day localized warming to year-long El Niños

Abstract

During the last 4 decades punctual occurrences of extreme ocean temperatures, known as marine heatwaves (MHWs), have been regularly disrupting the coastal ecosystem of the Peru-Chile eastern boundary upwelling system. In fact, this coastal system and biodiversity hot-spot is regularly impacted by El Niño events, whose variability has been related to the longest and most intense MHWs in the world ocean. However the intensively studied El Niños tend to overshadow the MHWs of shorter duration that are significantly more common in the region. Using sea surface temperature data from 1982 to 2019 we investigate the characteristics and evolution of MHWs, distinguishing events by duration. Results show that long duration MHWs (> 100 days) preferentially affect the coastal domain north of 15° S and have decreased in both occurrence and intensity in the last four decades. On the other hand, shorter events, which represent more than 90% of all the observed MHWs, are more common south of 15° S and show an increase in their thermal impact as well as on the number of affected days, particularly those spanning 30–100 days. We also show that long duration MHWs variability in the coastal domain is well correlated with the remote equatorial variability while the onset of short events (< 10 days) generally goes along with a relaxation of the local coastal wind.

Disentangling species-specific krill responses to local oceanography and predator’s biomass: The case of the Humboldt krill and the Peruvian anchovy

“…Extreme El Niño (Cai et al, 2018) and La Niña (Cai et al, 2015) events are also expected to increase in frequency due to climate change. Marine heatwaves (spanning 30-100 days) also show an increase in intensity and duration in the last decades in the HCS (Pietri et al, 2021). It is plausible to expect shifts in species distribution associated with these extreme events.…”

Marine heatwaves in shallow coastal ecosystems are coupled with the atmosphere: Insights from half a century of daily in situ temperature records

“…Work by Schlegel et al (2017a) using in situ coastal data records found that the coastal MHWs detected were typically associated with onshore or alongshore winds and anomalously high air temperature, with direct atmospheric forcing of coastal MHWs singled out as a driver that requires further investigation. Local wind relaxation events in upwelling zones have also recently been found to establish short-lived MHWs in coastal regions (Pietri et al, 2021). Further, it is apparent that the drivers of MHW occurrence can vary considerably with distance from the coastline.…”

Global Warming has Increased the Distance Traveled by Marine Heatwaves

“…For example, MHWs lasted for 251 days from 2015 to 2016 and reached a maximum intensity of 2.9°C above the climatology over the Tasman Sea (Oliver et al., 2017). A total of 426 MHWs were identified over the west coast of South America from 1982 to 2019, which lasted from 5 to 610 days and spatially covered 625–5,625,000 km 2 (Pietri et al., 2021). On a global scale, MHW duration and intensity increased by 84% and 65%, respectively, between 1982–1998 and 2000–2016 (Oliver et al., 2018).…”