Assessing the role of ICESat-2 in understanding Coastal Sea-Level

Abstract:

Since October of 2018, the photon counting Lidar onboard the ICESat-2 satellite has been measuring global ice, ocean, and land elevations. Laser pulses illuminate 3 pairs of tracks, with each track 15 m wide and spaced ~90 m apart. This is a substantial improvement in spatial resolution as compared to sea surface heights measured by conventional radar altimetry, which has an across-track footprint size of several kilometers. Measurements from radar altimetry and associated geophysical corrections are thus contaminated by land returns near the coast, leaving a spatial gap between tide gauges and altimeter observations. Here we explore the potential for the recent ATL12 ocean surface height product derived from ICESat-2 observations to bridge this gap. We first present overall statistical results comparing sea-level change rates estimated from tide gauges, ICESat-2, and along-track JASON-3 data. Next, we perform an in-depth comparison at tide gauges with exceptionally high agreement by considering vertical land motion over the ICESat-2 time frame. By analyzing both available GPS vertical heights and ICESat-2 elevation observations over land, we assess the extent to which vertical land motion affects the relative sea-level measurements recorded in tide gauges on short time scales (~ 2 years). In addition to global comparisons, we consider geographic areas separately to better understand the role of spatially varying oceanic and atmospheric processes in regional sea-level variability. We also investigate ICESat-2’s ability to distinguish wave characteristics from background ocean variability by analyzing the Sundra Strait Tsunami that devastated Indonesia in 2018. In addition to being valuable for tsunami modeling studies, wave detection and tracking are important for understanding the coherent characteristics of coastal sea-level variability. Overall, we present a broad survey of coastal sea-level observations that show generally good agreement, improving our understanding of the small-scale processes contributing to regional sea-level variability.