03 Aug 2023
 | 03 Aug 2023
Status: this preprint is open for discussion.

Investigating extreme marine summers in the Mediterranean Sea

Dimitra Denaxa, Gerasimos Korres, Emmanouil Flaounas, and Maria Hatzaki

Abstract. The Mediterranean Sea (MS) has been experiencing significant surface warming, particularly pronounced during summers and associated with devastating impacts. Τhis study proposes the concept of Extreme Marine Summers (EMSs) and investigates their characteristics in the MS, using Sea Surface Temperature (SST) reanalysis data spanning 1950–2020. A marine summer may evolve as extreme, in terms of mean summer SST, under different SST substructures. Results suggest that EMSs identified in most of the basin, are formed mainly due to the warmest part of the ranked daily SST distribution being warmer than normal. Areas where the warmest (coldest) part of the ranked daily SST distribution is more variable, experience EMSs primarily due to the contribution of the warmest (coldest) part of the distribution. Marine heatwaves (MHWs) within EMSs are more intense, longer lasting, and more frequent than usual, mainly in northern MS regions. However, the relative contribution of MHWs in EMSs is more pronounced in the central and eastern basin. Furthermore, a metric is proposed to quantify the driving role of air-sea heat fluxes in forming EMSs. Results suggest that surface fluxes primarily drive EMSs in the northern half of the MS, while oceanic processes play a major role in southern regions. Upper ocean preconditioning is also found to contribute to the EMS formation. Finally, a detrended dataset was produced to examine how the SST multi-decadal variability affects the studied EMS features. Despite leading to warmer EMSs basin-wide, the multi-decadal signal does not significantly affect the dominant SST substructures during EMSs. Results also highlight the fundamental role of latent heat flux in modulating the surface heat budget during EMSs, regardless of long-term trends.

Dimitra Denaxa et al.

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1709', Anonymous Referee #1, 31 Aug 2023 reply
  • RC2: 'Comment on egusphere-2023-1709', Anonymous Referee #2, 01 Oct 2023 reply

Dimitra Denaxa et al.

Dimitra Denaxa et al.


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Short summary
This study explores Extreme Marine Summers (EMSs) in the Mediterranean Sea using Sea Surface Temperature (SST) data. EMSs arise mainly due to the warmest summer days being unusually warm. Air-sea heat fluxes drive EMSs in northern regions, where also marine heatwaves (MHWs) highly contribute. Long-term SST changes lead to warmer EMSs and more intense MHWs, while not affecting the way daily SST values are organized during EMSs. Findings help understanding anomalously warm conditions in the basin.