Sea-Level Dynamics and Climate Impact in Caspian and Black Sea Regions

The Caspian and Black Sea basins represent a complex system of inland sea dynamics shaped by climatic forcing, catchment hydrology and palaeogeographic evolution. The Caspian Sea, the world’s largest endorheic basin, oscillates in level according to the balance between river inflow—primarily from the Volga, Kura and other rivers—and evaporation, which is highly sensitive to regional temperature and atmospheric circulation changes. The Black Sea, intermittently connected to the Mediterranean through the Bosphorus and Marmara gateways, has undergone dramatic transgressive–regressive cycles driven by glacial–interglacial shifts, sea-level changes in the world ocean and freshwater influx. Together, these basins host unique biota and support critical coastal infrastructure, fisheries and navigation routes. Sea-level variability in this region not only records past climate fluctuations—from Marine Isotope Stage 5 through the Holocene—but also presages future social, economic and ecological challenges as global temperatures rise.

Research from Nature Portfolio

Recent studies have applied state-of-the-art climate models to project 21st-century trends in the Caspian Sea extent. Model intercomparisons reveal that enhanced evaporation under mid-range greenhouse-gas scenarios will outpace precipitation across the Caspian catchment, leading to mean sea-level declines of the order of 8 metres by 2100, with worst-case scenarios exceeding 14 metres. Such reductions would desiccate the northern lowlands, threatening ecosystems, transport corridors and urban water supplies. A companion analysis broadens this perspective by emphasising that inland seas globally—if subject to the same hydrological imbalance—face parallel crises of biodiversity loss and geopolitical tension. Together, these contributions call for heightened awareness of the cascading impacts of climate-driven water-level changes on endemic species, coastal communities and regional stability.

Sea-Level Dynamics and Climate Impact in Caspian and Black Sea Regions publication trend

The graph below shows the total number of articles in sea-level dynamics and climate impact in caspian and black sea regions across all publications each year (not limited to Nature Index journals).

Technical terms

Endorheic basin: A closed drainage system that retains water, lacking natural outflow to the sea.

Inverted barometer effect: Change in sea-level height in response to variations in atmospheric pressure.

Shared Socioeconomic Pathway (SSP): A scenario framework outlining plausible trajectories of greenhouse-gas emissions and socio-economic development.

Sea-level anomaly (SLA): The departure of instantaneous sea-surface height from a long-term mean reference.

Transgressive-regressive cycle: Alternating phases of marine or lacustrine flooding and retreat over a land surface.

CMIP6: The sixth phase of the Coupled Model Intercomparison Project, providing coordinated climate model projections.

References

1. Climate-driven 21st century Caspian Sea level decline estimated from CMIP6 projections. Communications Earth & Environment (2023).
2. The other side of sea level change. Communications Earth & Environment (2020).
3. Caspian Sea Level Change Observed by Satellite Altimetry. Remote Sensing (2023).
4. Caspian — Black Sea Connection During MIS 5 (Late Pleistocene): Evidences from Drilling Data. Earth Systems and Environment (2025).
5. Quaternary time scales for the Pontocaspian domain: Interbasinal connectivity and faunal evolution. Earth-Science Reviews (2019).