'''DEFINITION'''

The medsea_omi_tempsal_sst_area_averaged_anomalies product for 2022 includes unfiltered Sea Surface Temperature (SST) anomalies, given as monthly mean time series starting on 1993 and averaged over the Mediterranean Sea, and 24-month filtered SST anomalies, obtained by using the X11-seasonal adjustment procedure (see e.g. Pezzulli et al., 2005; Pisano et al., 2020). This OMI is derived from the CMEMS Reprocessed Mediterranean L4 SST satellite product (SST_MED_SST_L4_REP_OBSERVATIONS_010_021, see also the OMI QUID, http://marine.copernicus.eu/documents/QUID/CMEMS-OMI-QUID-MEDSEA-SST.pdf), which provides the SSTs used to compute the evolution of SST anomalies (unfiltered and filtered) over the Mediterranean Sea. This reprocessed product consists of daily (nighttime) optimally interpolated 0.05° grid resolution SST maps over the Mediterranean Sea built from the ESA Climate Change Initiative (CCI) (Merchant et al., 2019) and Copernicus Climate Change Service (C3S) initiatives, including also an adjusted version of the AVHRR Pathfinder dataset version 5.3 (Saha et al., 2018) to increase the input observation coverage. Anomalies are computed against the 1993-2014 reference period. The reference for this OMI can be found in the first and second issue of the Copernicus Marine Service Ocean State Report (OSR), Section 1.1 (Roquet et al., 2016; Mulet et al., 2018).

'''CONTEXT'''

Sea surface temperature (SST) is a key climate variable since it deeply contributes in regulating climate and its variability (Deser et al., 2010). SST is then essential to monitor and characterise the state of the global climate system (GCOS 2010). Long-term SST variability, from interannual to (multi-)decadal timescales, provides insight into the slow variations/changes in SST, i.e. the temperature trend (e.g., Pezzulli et al., 2005). In addition, on shorter timescales, SST anomalies become an essential indicator for extreme events, as e.g. marine heatwaves (Hobday et al., 2018). The Mediterranean Sea is a climate change hotspot (Giorgi F., 2006). Indeed, Mediterranean SST has experienced a continuous warming trend since the beginning of 1980s (e.g., Pisano et al., 2020; Pastor et al., 2020). Specifically, since the beginning of the 21st century (from 2000 onward), the Mediterranean Sea featured the highest SSTs and this warming trend is expected to continue throughout the 21st century (Kirtman et al., 2013).

'''CMEMS KEY FINDINGS'''

During 2022, the Mediterranean Sea experienced an unprecedented long-lasting period of intense sea surface temperatures’ warming or, in other words, an exceptional marine heatwave event. The basin average SST anomaly was 0.8 ± 0.3 °C in 2022, well above the value of 0.5 ± 0.2 °C recorded in 2021. The Mediterranean SST warming started in May 2022, when the mean anomaly increased abruptly from 0.01 °C (April) to 0.76 °C (May), reaching the highest values during June (1.66 °C) and July (1.52 °C), and persisting until the end of the year with anomalies around 1 °C above the 1993-2014 climatology. The peak of June 2022 set the record of highest SST anomaly ever recorded since 1993. The 2022 Mediterranean marine heatwave is comparable to that occurred in 2003 (see e.g. Olita et al., 2007) in terms of anomaly magnitude but longer in duration: it lasted about seven months (May-December 2022) compared to the three of 2003 summer event (June-September 2003).

Over the period 1993-2022, the Mediterranean SST has warmed at a rate of 0.034 ± 0.002 °C/year, which corresponds to an average increase of about 1 °C during these last 30 years. Within its error (namely, the 95% confidence interval), this warming trend is consistent with recent trend estimates in the Mediterranean Sea (Pisano et al., 2020; Pastor et al., 2020). However, though the linear trend being constantly increasing during the whole period, the picture of the Mediterranean SST trend in 2022 seems to reveal a restarting after the pause occurred in the last years (since 2015-2021).

'''DOI (product):'''

https://doi.org/10.48670/moi-00268