Fig. 4: Geometries and analysis of the longest series of ribs from the top of the bump.
From: Rapid retreat of Thwaites Glacier in the pre-satellite era
a, Mean-adjusted composite topographic profile through the longest series of sea-floor ridges (see profile Y-Z’ in Fig. 3h for location). b, Extracted geometries (Methods) from a showing the longitudinal variability in height (orange) and spacing (blue) of 164 ribs plotted together with the output from the tide model28 (black; Methods). Alternating pink bars are 14-day periods, with blue triangles marking monthly intervals in the series (30.4 days). c, Periodograms (fast Fourier transforms) of the datasets in b showing the significance of frequencies in the series (cycles per day). Coloured circles mark the dominant peaks in the frequency spectra of the tidal model (grey), ridge amplitude data (orange) and ridge spacing data (blue), respectively. The tidal periodicity of 14.33 days in the tide model is the recurrence interval for spring and neap tides due to the interaction of principal lunar and principal solar semidiurnal tides. Red dashed line marks the Mf (lunar fortnightly) constituent.
