Upper-Ocean Contribution to Short-Term Regional Coastal Sea Level Variability along the United States

The upper ocean thermal structure is largely influenced by natural internal variability, and it modulates global surface temperature as well as regional sea level anomalies over decadal time scales. The internal variability of some important oceanographic processes, such as the Pacific decadal oscillation, can cause differences of 10 to 20 cm relative to the global mean in many coastal locations. These differences are sufficient to alter decisions between soft and/or large protective measures on every coast. Yet, current indicators of sea level changes are based on either surface variables or subsurface ocean measurements through the entire water column. There is also a lack of focus on short-term predictions of sea level change and concrete applications of these predictions at regional scale, which clouds local decision-making. The results herein confirm that the information contained within the top 300 m of the ocean is essential to capture decadal, regional relative sea level variability, whereas depths well below the thermocline do not appear to be closely tied to these large oscillations. Hence, the authors propose a regionally scoped indicator based on upper-ocean temperature as a first step toward identifying trend changes in short-term sea level rise over large coastal regions of the United States. The proposed indicator is a promising new tool that could help close the gaps mentioned above and improve the utility of existing local sea level records.