Understanding of Contemporary Regional Sea‐Level Change and the Implications for the Future

Abstract

Global sea level provides an important indicator of the state of the warming climate, but changes in regional sea level are most relevant for coastal communities around the world. With improvements to the sea‐level observing system, the knowledge of regional sea‐level change has advanced dramatically in recent years. Satellite measurements coupled with in situ observations have allowed for comprehensive study and improved understanding of the diverse set of drivers that lead to variations in sea level in space and time. Despite the advances, gaps in the understanding of contemporary sea‐level change remain and inhibit the ability to predict how the relevant processes may lead to future change. These gaps arise in part due to the complexity of the linkages between the drivers of sea‐level change. Here we review the individual processes which lead to sea‐level change and then describe how they combine and vary regionally. The intent of the paper is to provide an overview of the current state of understanding of the processes that cause regional sea‐level change and to identify and discuss limitations and uncertainty in our understanding of these processes. Areas where the lack of understanding or gaps in knowledge inhibit the ability to provide the needed information for comprehensive planning efforts are of particular focus. Finally, a goal of this paper is to highlight the role of the expanded sea‐level observation network—particularly as related to satellite observations—in the improved scientific understanding of the contributors to regional sea‐level change.

Past, Present, and Future Pacific Sea‐Level Change

“…10.1029/2020EF001839 6 of 14 Hamlington et al, 2020). The sea-level contribution from ocean mass change is higher in the western tropical Pacific than the US West Coast, again consistent with the expectation from the GRD response to ice mass loss during the altimeter era (e.g., Adhikari et al, 2016;B. D. Hamlington et al, 2020), but much lower in magnitude compared to the contribution from sterodynamic variability.…”

Coastal sea level anomalies and associated trends from Jason satellite altimetry over 2002–2018

“…Coastal zones are indeed densely populated and concentrate important infrastructures such as harbors and industries. While the causes of the global and regional sea level changes are now well known and reasonably well quantified 3 , 4 , 6 , 11 , 12 , additional small scale processes of oceanographic and hydrological origin, specific to coastal areas, may superimpose on the global and regional components, eventually modifying the rate of sea level rise close to the coast compared to the open ocean 13 , 14 . Potential coastal process able to modify sea level trends at the coast include local atmospheric effects, baroclinic instabilities, coastal trapped waves, shelf currents, waves, fresh water input from rivers in estuaries.…”

Evolving tides aggravate nuisance flooding along the U.S. coastline

“…Global mean sea level rose at an average rate of 3.3 ± 0.3 mm/year between 1993 and 2014 with an acceleration of 0.084 ± 0.025 mm/year 2 ( 19 , 20 ), thereby reducing the gap between high water levels and flood thresholds ( 3 , 11 , 15 , 17 , 21 ). Strong regional and local variability in sea-level rise and therefore NF trends are due to the global redistribution of water, large variability in vertical land motion, and other factors ( 22 ). Even within an individual estuary, subsidence rates can differ by up to 1 m/century ( 23 , 24 ), and accelerating sea-level rise will likely bring a precipitous increase in the number and duration of NF events ( 2 , 3 , 15 , 25 ).…”