Understanding the cause of sea level rise along coastal zone for 2005–2021

Abstract

Understanding the coastal sea level budget (SLB) is essential to revealing the causes of sea level rise and predicting future sea level change. Here we present the coastal SLB based on multiple sets of sea level observations, including satellite altimetry, satellite gravimetry, and Argo floats over 2005 to 2021. The coastal zone is defined within 500 km from the coast and covered by all Argo products. We find that sea level observations enable a closure for the coastal SLB for 2005-2015. However, since 2016, the coastal SLB shows a substantially larger discrepancy, consistent with the global mean SLB. The coastal SLB is unclosed for 2005-2021, with a mean sea level rise of 4.06 ± 0.27 mm yr−1, a 0.74 ± 0.21 mm yr−1 rate for ocean mass, and a 2.27 ± 0.53 mm yr−1 for the steric component. Systematic Argo buoy salinity drift after 2016 is the main cause for the non-closure of coastal SLB over 2005-2021. Ignoring the suddenly unrealistic coastal salinity trends, the global coastal SLB from 2005 to 2021 is closed with a residual trend of 0.46 ± 0.63 mm yr−1. Our results confirm that the coastal 500 km range does not need to be deliberately masked and ignored in global SLB research.