Forcing Factors Affecting Sea Level Changes at the Coast

TLDR

Sea‑level variability spans all timescales, with higher‑frequency processes amplified at coastlines by resonance and shallow‑water dynamics, making coastal signals more complex and often better captured by tide gauges, yet many aspects—such as the influence of wave setup and river runoff on historical mean records—remain under‑researched. The study reviews coastal sea‑level variability characteristics and highlights gaps in understanding how processes like wave setup and river runoff influence historical mean records used in climate research. The authors conduct a literature review comparing coastal sea‑level variability to that of the adjacent deep ocean.

Abstract

We review the characteristics of sea level variability at the coast focussing on how it differs from the variability in the nearby deep ocean. Sea level variability occurs on all timescales, with processes at higher frequencies tending to have a larger magnitude at the coast due to resonance and other dynamics. In the case of some processes, such as the tides, the presence of the coast and the shallow waters of the shelves results in the processes being considerably more complex than offshore. However, ‘coastal variability’ should not always be considered as ‘short spatial scale variability’ but can be the result of signals transmitted along the coast from 1000s km away. Fortunately, thanks to tide gauges being necessarily located at the coast, many aspects of coastal sea level variability can be claimed to be better understood than those in the deep ocean. Nevertheless, certain aspects of coastal variability remain under-researched, including how changes in some processes (e.g., wave setup, river runoff) may have contributed to the historical mean sea level records obtained from tide gauges which are now used routinely in large-scale climate research.