EOMF-09. Understanding Future Regional Sea Level Change Using Observation-Driven Extrapolations

Abstract
Global sea level is changing due to thermal expansion of the oceans (~1 mm/yr on average), and melting ice complexes (~1 mm/yr from ice sheets and ~1 mm/yr from glaciers; e.g., Hamlington et al., 2020). Although recent study has shown that global mean sea level is well approximated by a quadratic with rate and acceleration equal to ~3 mm/yr and ~0.1 mm/yr2, significant variations of sea level change arise on regional scales (e.g., rates may be 4x larger than this). Projections that include regional variations are essential to adaptation, mitigation and sustainable development in coastal cities, so we present one such projection in the following. Regional variations in sea level change are produced by (i) ocean dynamics, which unevenly distribute heat and thus thermal expansion of the oceans; and (ii) the gravitational, rotational and deformational response of the Earth to melting ice complexes (i.e., fingerprints), which cause regional uplift of the land around ice complexes as well as a regional reduction in the geoid to which sea level conforms, the ultimate result of which is sea level fall around melting ice complexes and enhanced sea level rise far away from melting ice complexes. However, the fingerprint signal from melting ice complexes has only recently been observed for the first time (Adhikari et al., 2019; Coulson et al., 2022). Therefore, a projection of altimeter-measured changes in absolute sea level, if projected in time, may not accurately resolve the future contribution to sea level change from ice complexes, which we expect will significantly dominate the steric component as time evolves. In this study, we project the sea level change associated with steric changes and that associated with the fingerprints of melting ice complexes, independently. The result is a new map of sea level change projected to 2050 including regional variations and an improved treatment of sea level rise from melting ice complexes. Adhikari, S., Ivins, E. R., Frederikse, T., Landerer, F. W., and Caron, L.: Sea-level fingerprints emergent from GRACE mission data, Earth Syst. Sci. Data, 11, 629–646, https://doi.org/10.5194/essd-11-629-2019, 2019. Coulson S, Dangendorf S, Mitrovica JX, Tamisiea ME, Pan L, Sandwell DT. A detection of the sea level fingerprint of Greenland Ice Sheet melt. Science. 2022 Sep 30;377(6614):1550-1554. doi: 10.1126/science.abo0926. Epub 2022 Sep 29. PMID: 36173832.