The Caspian Sea is the world’s largest land-locked lake. It plays a key role in the
Pontocaspian region, with a unique ecosystem providing numerous ecosystem services to
millions of people. Large variations in Caspian Sea level have occurred in the past and are
projected for the future. However, there is considerable debate about the importance of
different drivers and feedbacks leading to these variations. The primary aim of this thesis is
to use a modelling approach to improve our understanding of Caspian Sea hydroclimate and
sea level from the late Quaternary to the end of the 21st century.
Firstly, contributions to Caspian Sea level from glacial-interglacial climate change,
topographic changes due to ice-sheet loading, and ice-sheet meltwater were explored by
combining climate model simulations and ice-sheet reconstructions to drive a hydrological
model. The results show that the reorganization of river drainage systems due to
Fennoscandian ice-sheet growth and retreat played the dominant role in the variation of the
Caspian Sea level in the late glacial high-stand, while hydroclimate change was the major
factor leading to the early Holocene low-stand.
Secondly, given that large changes inCaspian Sea area will accompany changes in sea level,
a separate climate model experiment examined the extent and magnitude of subsequent
climate feedbacks. Results indicate an important local negative lake surface-evaporation
feedback and remote teleconnections, impacting as far as the North Pacific. This also
demonstrates the need for accurate representation of the Caspian Sea in climate models.
Finally, a hydrological balance model was used to explore future Caspian Sea level changes
based on multi-model climate projections from the Coupled Model Intercomparison Project
(CMIP5 and CMIP6) and idealized water extraction scenarios. The combined impacts of
anthropogenic warming and water withdrawals will lead to a decline in Caspian Sea level and
the desiccation of the shallow northern Caspian Sea before 2100. This will have multifaceted
implications for the surrounding communities, increasing freshwater scarcity, transforming
ecosystems, and impacting the climate system