Arctic Sea Level Variability from Oceanic Reanalysis and Observations

Quantifying the contributions to Arctic sea level (ASL) variability is critical to understand how the Arctic is responsing to ongoing climate change. Here, we use Ocean Reanalysis System 5 (ORAS5) reanalysis data and tide gauge and satellite altimetry observations to quantify contributions from different physical processes on the ASL variability. The ORAS5 reanalysis shows that the ASL is rising with a trend of 2.5 +/- 0.3 mm yr-1 (95% confidence level) over 1979-2018, which can be attributed to four components: (i) the dominant component from the global sea level increase of 1.9 +/- 0.5 mm yr-1, explaining 69.7% of the total variance of the ASL time series; (ii) the Arctic Oscillation-induced mass redistribution between the deep central basin and shallow shelves, with no significant trend and explaining 6.3% of the total variance; (iii) the steric sea level increase centering on the Beaufort Gyre region with a trend of 0.5 +/- 0.1 mm yr-1 and explaining 29.1% of the total variance of the ASL time series; and (iv) the intrusion of Pacific water into the Arctic Ocean, with no significant trend and contributing 14.2% of the total ASL variability. Furthermore, the dramatic sea ice melting and the larger area of open water changes the impact of the large-scale atmospheric forcing on the ASL variability after 1995, and the ocean dynamic circulation plays a more important role in the ASL variability.