Sea Level Rise: Analysis Results, and Variability within the Water Column

Abstract:

This work has two major thrusts: 1) Determination of sea level rise (SLR) from 700 to 2000m, and 2) the investigation of SLR variability as a function of depth using singular spectrum analysis (SSA) and Multi-Channel Singular Spectrum Analysis (M-SSA) techniques. We use the analysis of (Llovel, 2014) to study three different slices of the ocean as a function of depths, 0-700m, 0-2000, and 700-2000m. The contribution from 700-2000m was 0.38 +/- 0.05 mm/yr, a significant amount explaining in part the current hiatus. Wavelet analysis and SSA were used to study the time dependence; values of the first three periods were the same within the uncertainty considered in all three cases. In both the SSA and M-SSA, the first 8 modes were calculated. Llovel et al. (2014) found the contribution below 2000m was consistent with zero, when the uncertainties were considered.

Internal variability of the ocean is investigated as a function of depth using M-SSA and Wavelet analysis. Here we consider the ocean to have 58 layers covering the top 2000 m of the ocean with higher resolution near the surface. Each one of the ocean layers is considered a different channel (58 channels in total), which is analyzed as a function of time. The first mode was the largest and had the most robust signal active throughout the full column (0-2000m) with a period that is larger than the data series span. Modes 2-8 are concentrated near the surface. They appears have two ribbons of variability. The first signal is at sea level down to about 120-170 m; below the first ribbon, the second ribbon exists from 120-170 m down to 300-500 m. These results are similar to those of Nieves et al., 2015, where they focused on longer time-scales. The results of these analyses will be presented with their implications explained.