Effects of the basin dynamics on sea level rise in the Black Sea

Abstract

Abstract. Satellite altimetry measurements show that magnitude of the Black Sea level trends is spatially uneven. While the basin-averaged sea level was increasing at a rate of 3.15 mm/year from 1993 to 2014, the sea level rise varied from 0.15–2.5 mm/year in the central part to 3.5–3.8 mm/year in coastal areas and 5 mm/year in the southwestern part of the sea. These differences are caused by changes in the large- and mesoscale circulation of the Black Sea. A long-term increase of the cyclonic wind curl over the basin from 1979 to 2014 strengthened divergence in the center of the Black Sea that led to an increase of sea level near the coast and a decrease in the center of the basin. Changes in the distribution and intensity of mesoscale eddies caused the formation of the local extremes of sea level trend. The variability of the dynamic sea level (DSL) – the difference between the local and the basin-averaged sea levels – contributes significantly (up to ~ 50 % of the total variance) to the seasonal and interannual variability of sea level in the basin. The DSL variability in the Black Sea depends strongly on the basin-averaged wind curl and is well reconstructed using the ERA-Interim winds from 1979 to present, including the time when altimetry data was unavailable. The reconstruction can be used to correct historical tide gauges data for dynamic effects, which are usually neglected in the analysis of the Black Sea tide gauge records.

The Black Sea level trends according to altimetry data after removing dynamic noise

“…The Black Sea mean level trend, based on altimetry data was estimated at 3.2 ± 0.6 mm/year for 1993-2014 [4]. Taking into account the slower growth of the level after 2014 the trend of the Black Sea average level was 2.5±0.5 mm/year for the period 1993-2017 [5].…”

“…It is noted that the level trend values are heterogeneously distributed across the Black Sea and the trends in the Black Sea coastal area are about 1.5-2 times higher than in the deep-sea part of the basin. This is due to the inter-annual variability of the Black Sea the dynamics and the redistribution of water masses within the basin [4,5]. A general approach of the trend assessment in the coastal zones of the World's oceans is presented in [6].…”