Benjamin Hamlington - (Jet Propulsion Laboratory)


Christopher Piecuch (Woods Hole Oceanographic Institution)
Fabian Schloesser (University of Hawaii, Honolulu)
Philip Thompson (University of Hawaii, Honolulu)


With the launch and future operations of Sentinel-6A/Michael Freilich, the modern altimeter record will extend past three decades in length. This continuous record with near-global coverage has yielded a precise estimate of an increase in global mean sea level, while offering a clear depiction of the spatial variability in sea level change around the world. As a result of the increasing length of the altimeter record, studies have sought to understand and detect the emergence of a forced or anthropogenic response in sea level. The central idea behind these studies is that the altimeter record is now long enough that the influence of interannual to decadal variability is reduced and does not serve to obscure an underlying trend in the way that it did for most of the altimeter record. With the now 26-year altimeter record, however, there is still great spatial variability in the regional trend pattern. For the altimeter pattern to be representative of trends expected to continue into the future, this spatial variability would have to arise – at least in large part – from anthropogenic forcing.

In this project, we seek to investigate the degree to which this is true by performing a comprehensive, detailed study into the regional satellite altimeter trends. Our project is centered around three particular questions: 1.Will the satellite altimeter trends change as the record extends past three decades in length with the launch of Sentinel-6A/Michael Freilich? 2. In what parts of the ocean will the satellite-altimeter trends be similar or different as the record lengthens? 3. What are the processes - both natural and forced - that are impacting satellite altimeter-measured trends? To answer these questions, we will perform targeted statistical analyses on the lengthening satellite altimeter record, focusing on the contributions of shorter-term variability and the evolution of regional trends over the past three decades. Similar analyses will also be performed on the longer record provided by tide gauges to provide context for the satellite altimeter record. These observation-driven studies will be complemented by ECCO- and model-based investigations into the processes - both natural and forced - that can impact regional sea level trends. We are interested in determining the relative roles of natural and forced variability and assessing the extent to which the trends measured during the altimeter era will persist into the future. Similar to what has been done for regional trends in terrestrial water storage measured by GRACE, our goal is to identify prominent features in the altimeter trend map and understand the processes that drive those features.

Through this project, we expect to demonstrate the value and importance of the lengthening altimeter record that includes new observations from Sentinel-6A/Michael Freilich. We expect to impact the state of knowledge by providing either observational support or opposition to the idea that the forced pattern of sea level rise has emerged. It is likely that the answer to this question varies regionally, and through our investigation, we will provide a better understanding of what drives sea level change on timescales approaching 30-years on the regional level.

Supported by NASA