Antarctic tides from GRACE satellite accelerations

Models are routinely used to remove the effects of global ocean tides from GRACE data during processing to reduce temporal aliasing into monthly GRACE solutions. These models have typically been derived using data from satellite altimeter missions such as TOPEX/Poseidon. Therefore the polar components of tide models aren't well constrained by altimetry data, potentially resulting in errors that are likely to alias into monthly GRACE gravity fields at all latitudes. Nine years of GRACE inter-satellite accelerations are inverted to solve for corrections to the amplitude and phase of major solar and lunar ocean tides at latitudes south of 50°S using a mascon approach. The tide model originally applied to the data was GOT4.7, truncated to maximum degree and order 90. Uncertainty estimates are derived from tidal solutions on land, and by subtracting two independent solutions that each use 4.5 years of data. Features in the M2, K1, S2, and O1 solutions that rise above the noise floor likely represent errors in the GOT4.7 model. This ill-posed problem requires regularization; Tikhonov damping and truncated SVD are compared. The regularization strength is optimized by calculating residuals for accelerations withheld from the inversion at different regularization strengths. This regularization limits the inversion's resolution, which is characterized at different latitudes.