New Evidence of Mediterranean Climate Change and Variability from Sea Surface Temperature Observations

Abstract

Estimating long-term modifications of the sea surface temperature (SST) is crucial for evaluating the current state of the oceans and to correctly assess the impact of climate change at regional scales. In this work, we analyze SST variations within the Mediterranean Sea and the adjacent Northeastern Atlantic box (west of the Strait of Gibraltar) over the last 37 years, by using a satellite-based dataset from the Copernicus Marine Environment Monitoring Service (CMEMS). We found a mean warming trend of 0.041 ± 0.006 ∘ C/year over the whole Mediterranean Sea from 1982 to 2018. The trend has an uneven spatial pattern, with values increasing from 0.036 ± 0.006 ∘ C/year in the western basin to 0.048 ± 0.006 ∘ C/year in the Levantine–Aegean basin. The Northeastern Atlantic box and the Mediterranean show a similar trend until the late 1990s. Afterwards, the Mediterranean SST continues to increase, whereas the Northeastern Atlantic box shows no significant trend, until ~2015. The observed change in the Mediterranean Sea affects not only the mean trend but also the amplitude of the Mediterranean seasonal signal, with consistent relative increase and decrease of summer and winter mean values, respectively, over the period considered. The analysis of SST changes occurred during the “satellite era” is further complemented by reconstructions also based on direct in situ SST measurements, i.e., the Extended Reconstructed SST (ERSST) and the Hadley Centre Sea Ice and Sea Surface Temperature dataset (HadISST), which go back to the 19th century. The analysis of these longer time series, covering the last 165 years, indicates that the increasing Mediterranean trend, observed during the CMEMS operational period, is consistent with the Atlantic Multidecadal Oscillation (AMO), as it closely follows the last increasing period of AMO. This coincidence occurs at least until 2007, when the apparent onset of the decreasing phase of AMO is not seen in the Mediterranean SST evolution.

Ecology, distribution and expansion of a Mediterranean native invader, the fireworm Hermodice carunculata (Annelida)

“…A consistent warming trend has been found for Mediterranean Sea surface temperatures (SST) in the 1982-2016 period, with a clear increase in the annual mean SST after 1993 especially in the eastern basins (Pastor et al, 2018;Pisano et al, 2020). The nearly continuous warming trend of the Mediterranean Sea accounts for a total SST increase of about 1.5°C from 1982 to 2018.…”

“…However, decadal and spatial analyses of SST variations highlighted that the warming rate is not uniform. Short local cooling trends were observed until 2005, but since then no pausing phases occurred in the overwhelming warming tendency (Pisano et al, 2020). At sub-basin level, the Western Mediterranean and the Ionian Seas show lower warming trends, while the most intense values are observed in the Adriatic Sea and in the Gulf of Taranto, which seem to reflect the greater increases in temperature in the Levantine-Aegean Sea (Pisano et al, 2020;Sakalli, 2017).…”

“…Although the Adriatic Sea is warming fast (Pisano et al, 2020), fireworm presence in BS8 only concerned the Croatian coasts. This may be due to the general surface circulation in the Adriatic basin, which brings Levantine and Ionian warm-waters northwards along the Croatian eastern coast, up to the Northern Adriatic where they are affected by the cold Bora wind effect before moving southward along the Italian west coast (Bergamasco & Malanotte-Rizzoli, 2010;Millot & Taupier-Letage, 2015).…”

A Warming Mediterranean: 38 Years of Increasing Sea Surface Temperature

“…In a recent paper, ref. [17] described similar values for SST trends, indicating 0.041 • C/year over the whole Mediterranean Sea from 1982 to 2018, with values from 0.036 • C/year in the western basin and 0.048 • C/year in the Levantine-Aegean basin, while a recent report from the Copernicus Marine Service [8] showed a warming trend of 0.04 • C/year for the whole Mediterranean basin. The results from all these studies agree with the consistent warming trend across the Mediterranean basin since the early 1980s, which leads us to think of anthropogenic warming in the context of global change.…”

“…SST participates in the mechanisms that trigger extreme weather events, such as medicanes [15,16], which could increase their intensity because of the projected SST and latent heat flux increases resulting from climate simulations [11]. As such, knowledge of SST past trend behavior can act as a good indicator of actual climate change [17], but also of possible future climate scenarios, especially in the Mediterranean area. A side question that will benefit from the improved knowledge on SST climatology and trends concerns the study of Marine Heat Waves (MHW), a topic still under discussion.…”