Understanding the Regional Disparity of the Sea Level Rise during Altimetry Era

The application of satellite altimetry allows us to acquire global sea level height data with higher spatial and temporal resolution, enabling a systematic understanding of spatial differences in sea level rise. In our study, we reconstructed the barystatic sea level and steric sea level change during the altimetry era (1993-2022). This involved utilizing mass change data and ocean heat content data from various sources. Notably, we incorporated the latest observation and model-simulation data, ensuring coverage of the entire altimetry era compared with previous reconstructions. Based on altimetry-observed relative sea level change, the global sea level rise rate is 3.38 [3.09 3.68] mm/yr, the global barystatic and steric sea level change is 1.80 [1.45 2.15] mm/my, and 1.02 [0.67 1.37] mm/yr, respectively. Subsequently, we further analyzed the regional characteristics of these sea level rises.

Over the past three decades, sea levels have exhibited a faster rate of increase in the western basins, as well as in the equatorial and mid-latitude region, surpassing the global average. Conversely, sea level rise at higher latitudes has been relatively slower than the global average. In the mid-low latitude regions, the higher rate of sea level rise is primarily dominated by the expansion of ocean water due to its heating. In high-latitude regions, the lower sea level rise rate is primarily attributed to the far-field effects of the melting of land ice. The distribution of halosteric sea level changes is nearly uniform across latitudes. However, in the western Atlantic, a significant counteracting effect against the rise in thermosteric sea level is observed. This is linked to the weakening Atlantic Meridional Overturning Circulation (AMOC).

Furthermore, we selected 8 regions, North Pacific (NP), South China Sea (SCS), Western Tropical Pacific (WTP), Bay of Bengal (BOB), Tropical Indian Ocean (TIO), Southwest Pacific (SWP), Gulf of Mexico (GOM), and North Atlantic (NA), with sea level rise rates faster than the global average. We analyzed the contributions of different components to the sea level rise in these areas. These regions are all adjacent to land or have a significant number of islands, the faster sea level rise poses a greater threat to the corresponding coastal areas. The contributions of barystatic and steric sea level components are approximately equal in most of these regions. However, in SCS and GOM, the contributions of the barystatic component exceed 60%. The halosteric sea level has a significant negative contribution to the sea level rise in the GOM and NA. The Antarctic Ice Sheet and Greenland Ice Sheet melting contribute to sea level rise in these regions by less than 15%, and more than 15%, respectively. The highest contribution of glacier melting is in the SCS, approximately 23%. Compared to the melting of land ice, changes in land water contribute limitedly to sea level rise in these regions. The contribution is less than 10%, except for in NA.