Steric and atmospheric contributions to interannual sea level variability in the eastern mediterranean sea over 1993–2019

Abstract

Sea level trends and their forcing over the eastern Mediterranean basin are investigated by using 27 years (1993–2019) of gridded sea level anomalies (SLA) derived from satellite altimetry and 9 tide gauge stations, along with sea surface temperature (SST) and temperature and salinity profiles. The contributions of atmospheric (wind and pressure) and steric components to the interannual variability of total SLA were evaluated. The thermosteric component represents the major contributor to the linear trend and was positive over most of the eastern Mediterranean, with a spatially averaged trend of 2.13±0.41 mm/year, accounting for 69% of the total sea level trend (3.1±0.61 mm/year). In contrast, the halosteric effect has a negative contribution to the steric SLA, with a mean trend of -0.75±0.19 mm/year. The atmospheric component trend was much lower at 0.32±0.24 mm/year. The interannual variability of SLA accounts for about 36% of overall sea level variability. Steric and atmospheric contributions to the interannual variability of sea level in the eastern Mediterranean account for about 52% and 18%, respectively. The strongest interannual variability and trends in SLA were observed over the basin's main recurrent gyres, with the maximum positive trend obtained over the Mersa–Matruh and Cyprus gyres, as well as the North Shikmona eddy, and maximum negative trend over the Ierapetra gyre. Over the study period, all tide gauges showed a positive and statistically significant trend, ranging from 1.47±0.77 to 5.79±1.32 mm/year after applying glacial isostatic adjustment and atmospheric correction, and were in good agreement with reconstructed steric sea level data.