System description

Marine heatwaves definition

Marine heatwaves (MHW) are extreme warm ocean temperatures during prolonged periods, when temperatures are warmer than the 90th percentile of the climatological distribution (so-called marine heat spike) for at least five consecutive days (Hobday et al., 2016). MHWs are increasing substantially in frequency, duration and intensity worldwide. In the Mediterranean Sea, the rapid sea surface warming trend has been associated with strong increase in MHW days, particularly during the last two decades (Bensoussan et al., 2019; Juza and Tintoré, 2021). MHWs have devasting impacts on ecosystem, threaten economies and strengthen storms by warming ocean waters.

Ocean datasets

MHWs are computed using sea surface temperature (SST) from satellite observations distributed by the Copernicus Marine Service. The Copernicus Marine Service Mediterranean product provides daily optimally interpolated estimates of SST in the Mediterranean (Pisano et al., 2016, Buongiorno Nardelli et al., 2013). The 10-day forecasts of SST from the Copernicus Marine Service Mediterranean Sea analysis and forecast model (Clementi et al., 2021) are also used. The Copernicus Marine Service products used are:
  • Near real-time satellite SST from 2020-01-01 to present (SST_MED_SST_L4_NRT_OBSERVATIONS_010_004)
  • Reprocessed satellite SST from 1982-01-01 to 2019-12-31 (SST_MED_SST_L4_REP_OBSERVATIONS_010_021)
  • Analysis and forecast SST over the current year (MEDSEA_ANALYSISFORECAST_PHY_006_013)
  • The daily mean and 90th percentile climatologies are built over the period 1982-2015 using the Copernicus Marine Service satellite reprocessed SST product.

    Sub-regional approach

    The MHW detection and long-term variability are provided in the different sub-regions of the Mediterranean Sea, as defined by Manca et al. (2004):


  • Bensoussan, N., Chiggiato, J., Buongiorno Nardelli, B., Pisano, A., Garrabou, J. (2019). Insights on 2017 Marine Heat Waves in the Mediterranean Sea. Copernicus Marine Service Ocean State Report : Issue 3. J. Op. Oceanogr., 12 (suppl.1): 101-108.
  • Buongiorno Nardelli, B., Tronconi, C., Pisano, A., Santoleri, R. (2013). High and Ultra-High resolution processing of satellite Sea Surface Temperature data over Southern European Seas in the framework of MyOcean project. Rem. Sens. Env., 129, 1-16, doi:10.1016/j.rse.2012.10.012.
  • Clementi, E., Aydogdu, A., Goglio, A.C., Pistoia, J., Escudier, R., Drudi, M., ... Pinardi, N. (2021). Mediterranean Sea Physical Analysis and Forecast (CMEMS MED-Currents, EAS6 system) (Version 1) [Data set]. Copernicus Monitoring Environment Marine Service (CMEMS).
  • Hobday, A.J., Alexander, L.V., Perkins, S.E., Smale, D.A., Straub, S.C., Oliver, E.C., ... Holbrook, N.J. (2016). A hierarchical approach to defining marine heatwaves. Prog. Oceanogr., 141, 227-238.
  • Juza, M. and Tintoré, J. (2021). Multivariate sub-regional ocean indicators in the Mediterranean Sea: from event detection to climate chage estimations. Front. Mar. Sci., 8:610589,
  • Manca, B., Burca, M., Giorgetti, A., Coatanoan, C., Garcia, M.J., Iona, A. (2004). Physical and biochemical averaged vertical profiles in the Mediterranean regions: an important tool to trace the climatology of water masses and to validate incoming data from operational oceanography. J. Mar. Sys., 48(1-4), 83-116.
  • Pisano, A., Nardelli, B.B., Tronconi, C., Santoleri, R. (2016). The new Mediterranean optimally interpolated pathfinder AVHRR SST Dataset (1982–2012). Remote Sens. Environ., 176, 107-116.