An Assessment Of Regional Icesat-2 Sea-Level Trends

Sea-level rise is an important indicator of ongoing climate change and well observed by satellite altimetry. However, observations from conventional altimetry degrade at the coast where regional sea-level changes can deviate from the open-ocean and impact local communities. With the 2018 launch of the laser altimeter onboard ICESat-2, new high-resolution observations of ice, land, and ocean elevations are available. Here we assess the potential benefits of sea level measured by ICESat-2 by comparing to data from Jason-3 and tide gauges. We find good agreement in the linear rates computed from the independent observations, with an absolute average residual of 3.60 0.03 cm yr(-1) between global ICESat-2 and Jason-3 observations at a 1 degrees posting. The recent La Nina is clearly evident in ICESat-2 observations, as well as small-scale features. By demonstrating the quality of the ICESat-2-measured sea level, we provide support for integrating it into the existing suite of sea-level observations.Plain Language Summary Sea levels are rising globally due to human induced climate change. However, local sea levels that impact coastal communities often differ from the global increase, sometimes by a factor of 2 or more. Unfortunately, measuring sea level along the coast can be challenging, as radar satellites are primarily designed for the open ocean. Additionally, direct measurements from tide gauge stations are typically spaced far apart, and thus don't adequately represent the full range of changes that occur along the coast. In 2018, NASA launched the ICESat-2 satellite which carries a laser instrument capable of measuring sea level much closer to the coast than existing radar satellites. Here we assess how well ICESat-2 data measures coastal sea level by comparing it to data from the radar satellite Jason-3 and tide gauges measurements. We find good agreement in recent sea-level changes computed from both data sources. Large-scale climate patterns, such as the recent La Nina, as well as small-scale oceanic features like currents are clearly evident in the ICESat-2 data. These results support the idea that ICESat-2 measurements can be integrated into the existing suite of sea-level observations and serve as an additional tool for addressing ongoing sea-level rise.Key PointsHigh spatial resolution sea-level observations from ICESat-2 are available over the global oceansSea-level trends computed from ICESat-2 observations agree with independent measurements from radar altimetry and tide gaugesUncertainty on the estimated trends is expected to decrease by an order of magnitude in 5 years through averaging