CoAuthors

J.T. Reager (NASA JPL, USA); Hrishi Chandanpurkar (NASA JPL, USA)

Since 2002, the Gravity Recovery and Climate Experiment (GRACE) mission has provided accurate measurements of variations in Earth’s gravity field, leading to new insights on a wide range of topics. Particular advancement has been made in our understanding of how water moves through the Earth System, with implications for understanding climate and human impacts. This movement of water is particularly relevant for the study of sea level on global scales. The two dominant drivers of changes in global mean sea level (GMSL) are thermal expansion due to the warming ocean, and changes in ocean mass associated with this water movement between land to ocean. With the addition of GRACE and the Argo profiling floats to the sea level observing network since 2002 and 2004, respectively, recent efforts have been made to “close the GMSL budget” through comparisons to satellite altimeter observations. While the combined global mean trends from GRACE and Argo agree reasonably well with the altimeter-measured GMSL, there is some disagreement on shorter timescales.

Additionally, despite the advances that have been made, the available record length limits our understanding. The GRACE mission ended in mid-2017, leaving the data record at only 15-years in length. To continue the record started by GRACE, the GRACE Follow-On (GRACE-FO) mission launched in 2018 with new data soon to be publicly released. However, the relatively short record from the two missions coupled with the gap between them still present challenges in examining long time-scale climate processes and limits budget studies to times when GRACE data is available. There have been numerous efforts to extend the steric sea level record prior to the Argo time period and thus infer the global change due to TWS, but there is considerable disagreement amongst the available steric products. A longer TWS record would allow for the evaluation of these steric datasets, while providing the opportunity to study the GMSL budget over the full length of the satellite altimeter record (1993 to present).

We apply a novel multivariate data analysis technique to meet the following objectives: 1) Extend the monthly data record of satellite-measured TWS back to 1979 to produce a dataset appropriate for studying lower-frequency natural variability, and 2) Fill gaps in the GRACE record to provide a continuous dataset of TWS from 2002 to 2017 that is consistent with GRACE measurements. This longer record of TWS allows for the study of longer-term natural variability that could impact the way we interpret the satellite sea level records, and allows for improved sea level budget studies that yield new insights into GMSL change.