Arctic Ocean Mass Variability From 2003 to 2019 Using GRACE and GRACE-FO Ocean Bottom Pressure Measurements.

The Gravity Recovery and Climate Experiment (GRACE) provided monthly global ocean bottom pressure (OBP) observations from March 2002 to June 2017. Its identical, follow-on mission, GRACE-FO, has been in orbit since 2018, and the first year of monthly GRACE-FO OBP data (July 2017 – June 2018) is now readily available. The goals of this work are two-fold: 1) to bridge the GRACE and GRACE-FO OBP observations in the Arctic, and 2) to track changes in OBP variability from 2002 to 2019, and their associated atmospheric forcing.

In order to bridge GRACE and GRACE-FO measurements of OBP, we combine the available in situ OBP data from the North Pole from 2005 to 2015 as part of the North Pole Environmental Program with in situ OBP data from the Canada Basin from 2003 to 2018 as part of the Beaufort Gyre Exploration Program, GRACE OBP from 2002 to 2017, and atmospheric reanalysis data from 2003 to 2019. We use statistical techniques such as empirical orthogonal functions, maximum co-variance analysis and simple linear regression models, to create a proxy representation of Arctic-wide OBP from 2017 to the present. We validate our proxy OBP field with the new GRACE-FO OBP data, and bridge GRACE and GRACE-FO observations in the entire Arctic Ocean. We then use the merged solution of Arctic-wide OBP to track changes in OBP variability and their associated ocean circulation variability since 2003.