Response of the sea surface temperature to heatwaves during the France 2022 meteorological summer

Abstract

Abstract. The summer of 2022 was memorable and record-breaking, ranking as the second hottest summer in France since 1900, with a seasonal surface air temperature average of 22.7 ∘C. In particular, France experienced multiple record-breaking heatwaves during the meteorological summer. As the main heat reservoir of the Earth system, the oceans are at the forefront of events of this magnitude which enhance oceanic disturbances such as marine heatwaves (MHWs). In this study, we investigate the sea surface temperature (SST) of French maritime basins using remotely sensed measurements to track the response of surface waters to the atmospheric heatwaves and determine the intensity of such feedback. Beyond the direct relationship between SSTs and surface air temperatures, we explore the leading atmospheric parameters affecting the upper-layer ocean heat budget. Despite some gaps in data availability, the SSTs measured during the meteorological summer of 2022 were record-breaking, the mean SST was between 1.3 and 2.6 ∘C above the long-term average (1982–2011), and the studied areas experienced between 4 and 22 d where the basin-averaged SSTs exceeded the maximum recorded basin-averaged SSTs from 1982 to 2011. We found a significant SST response during heatwave periods with maximum temperatures measured locally at 30.8 ∘C in the north-western Mediterranean Sea. Our results show that in August 2022 (31 July to 13 August), France experienced above-average surface solar radiation correlated with below-average total cloud cover and negative wind speed anomalies. Our attribution analysis based on a simplified mixed-layer heat budget highlights the critical role of ocean–atmosphere fluxes in initiating abnormally warm SSTs, while ocean mixing plays a crucial role in the cessation of such periods. We find that the 2 m temperatures and specific humidity that are consistently linked to the advection of warm and moist air masses are key variables across all the studied regions. Our results reveal that the influence of wind on heatwaves is variable and of secondary importance. Moreover, we observe that the incident solar radiation has a significant effect only on the Bay of Biscay (BB) and the English Channel (EC) areas. Our study findings are consistent with previous research and demonstrate the vulnerability of the Mediterranean Sea to the increasing frequency of extreme weather events resulting from climate change. Furthermore, our investigation reveals that the recurring heatwave episodes during the summer of 2022 had an undeniable impact on all the surveyed maritime areas in France. Our study therefore provides valuable insights into the complex mechanisms underlying the ocean–atmosphere interaction and demonstrates the need for an efficient and sustainable operational system combining polar-orbiting and geostationary satellites to monitor the alterations that threaten the oceans in the context of climate change.

Marine heatwaves on the rise: One of the strongest ever observed mass mortality event in temperate gorgonians

“…In the NW Mediterranean, these high-impact thermal anomalies are either characterized by short periods (2-5 days) with a mean temperature reaching 27°C and often associated with large diurnal variations or characterized by long durations (up to 1 month) at warm and stable temperature (23-24°C) (Crisci et al, 2011). During the summer of 2022, while record-breaking heatwaves hit Europe, the Western Mediterranean Sea experienced record high MHWs (Guinaldo et al, 2023). The sea surface temperature (SST) reached extreme hot values, up to 30°C in its northern part, while summer mean temperature anomalies as high as 4.6°C could be evidenced from satellite data (https://www.…”

Response of two temperate scleractinian corals to projected ocean warming and marine heatwaves

“…The use of the natural cycle of temperature data based on 9 years of in situ records is important to better understand the effects of extreme events that are increasing every year in frequency and intensity in the Mediterranean Sea. For example, recently, summer 2022 might have been one of the worst MHWs, with SST anomaly of +5°C along the coast of France and Italy [ 15 ]. Our results showed an impact of high temperature on the number of polyps and respiration for both species and on the symbiosis of C. caespitosa .…”

“…During the period 2015–2019, exceptional thermal conditions and MHWs in the Mediterranean Sea resulted in five consecutive years of widespread mass mortality events of marine species [ 5 ]. Recently, in 2022, western parts of the Mediterranean Sea have experienced the second hottest summer since the beginning of measurements, the hottest year being 2003 [ 15 ]. In 2022, the anomaly of SST between 1.3 and 2.6°C above the long-term average (1982–2011), and temperatures up to 30.8°C were recorded in August in the northwestern Mediterranean Sea [ 15 ].…”

“…Recently, in 2022, western parts of the Mediterranean Sea have experienced the second hottest summer since the beginning of measurements, the hottest year being 2003 [ 15 ]. In 2022, the anomaly of SST between 1.3 and 2.6°C above the long-term average (1982–2011), and temperatures up to 30.8°C were recorded in August in the northwestern Mediterranean Sea [ 15 ]. These extreme thermal events cause a long-term decline in habitat-forming species including corals and gorgonians that are among the most affected benthic organisms by MHWs [ 5 ].…”

Unveiling microbiome changes in Mediterranean octocorals during the 2022 marine heatwaves: quantifying key bacterial symbionts and potential pathogens

“…In particular, the Mediterranean Sea is turning into one of the fastest-warming seas on Earth, with temperatures rising 20% faster than the global average [ 14 , 52 , 66 ] and a high occurrence of MHWs over the past two decades [ 18 , 19 , 39 , 60 ]. In 2022, between three and seven record-breaking MHWs hit the Mediterranean Sea between May and September, with SST anomalies locally reaching 4.3 °C above the summer average, exceeding the previous maximum of +2–3 °C during the 2003 MHWs [ 33 , 73 , 92 ]. Recurrent MHWs have had devastating effects on community structure and health of marine animal forests (MAFs) [ 11 , 32 ], which are among the most biodiverse assemblages in the Mediterranean Sea [ 61 , 65 , 81 ].…”