Black Sea Surface Temperature time series and trend from Observations Reprocessing

"''DEFINITION'''

The blksea_omi_tempsal_sst_area_averaged_anomalies product for 2024 includes unfiltered Sea Surface Temperature (SST) anomalies, given as monthly mean time series starting on 1982 and averaged over the Black Sea, and 24-month filtered SST anomalies, obtained by using the X11-seasonal adjustment procedure. This OMI is derived from the CMEMS Reprocessed Black Sea L4 SST satellite product (SST_BS_SST_L4_REP_OBSERVATIONS_010_022, see e.g. the OMI QUID, http://marine.copernicus.eu/documents/QUID/CMEMS-OMI-QUID-BLKSEA-SST.pdf), which provided the SSTs used to compute the evolution of SST anomalies (unfiltered and filtered) over the Black Sea. This reprocessed product consists of daily (nighttime) optimally interpolated 0.05° grid resolution SST maps over the Black Sea built from the ESA Climate Change Initiative (CCI) (Embury et al., 2024) 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 1991-2020 reference period. The 30-year climatology 1991-2020 is defined according to the WMO recommendation (WMO, 2017) and recent U.S. National Oceanic and Atmospheric Administration practice (https://wmo.int/media/news/updated-30-year-reference-period-reflects-changing-climate). 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). In the last decades, since the availability of satellite data (beginning of 1980s), the Black Sea has experienced a warming trend in SST (see e.g. Buongiorno Nardelli et al., 2010; Mulet et al., 2018).

'''KEY FINDINGS'''

In 2024, the annual mean Sea Surface Temperature (SST) in the Black Sea was 17.2 °C, which is 1.8 °C above the 1991–2020 climatological average of 15.4 °C, and nearly 1 °C higher than the previous year's value of 16.5 °C. This marks the highest annual mean SST recorded in the region since 1982. Unlike previous years, all monthly mean SST anomalies in 2024 were positive, ranging from 1 to 3 °C. The largest anomaly, 3.2 °C, occurred in April, corresponding to a mean SST of 13.1 °C, while the smallest anomaly, 0.83 °C, was recorded in December, with a mean SST of 11.6 °C. Over the period 1982–2024, the Black Sea SST has increased at an average rate of 0.056 ± 0.003 °C per year, resulting in a total warming of approximately 2.4 °C over the past 43 years.

'''DOI (product):''' https://doi.org/10.48670/moi-00217