A Coastal Mean Sea Level and Sea Level Rise Product Derived from ICESat(-2) Laser Altimetry

Abstract:

Accelerating sea level rise is affecting coastal megacities across the globe. Projections of sea level rise (SLR) require accurate baseline observations. However, the mean coastal sea level is currently only well known in areas where tide gauges are well established and provide long term records. Many cities vulnerable to sea level rise do not have adequate long term tide gauge records.

Pulse-limited radar altimetry, such as the TOPEX/Poseidon and Jason series of satellites, has mapped global mean sea level (MSL) for nearly three decades. However, their measurements are contaminated and unusable near to the coastline. Coastal mean sea level may also vary significantly from the open ocean’s due to winds, currents, bathymetry and terrain effects. Changes occurring in the region between the coastline and the open ocean is of considerable interest for coastal cities across the world, and we use ICESat-2 to fill in the gap. ICESat-2 is a laser altimeter that was launched in 2018 and its small footprint (several meters vs pulse-limited altimetry’s kilometers) allows it to measure sea level much closer to the coast before being contaminated by land.

We present a coastal mean sea level product derived from the ICESat-2 ATL03 level 2 geolocated photon product. Additionally, we combine ICESat-2 with ICESat-1 laser altimetry, with measurements between 2003 and 2009, to determine data-driven trends in coastal sea level rise near coastal cities across the world, after validation with tide gauges.