| 05 Jun 2026
Topographic control of tides in the Ross Sea: eddy-like structures, bottom-trapped waves, and energetics
Abstract. Using a regional high-resolution coupled ocean-sea ice-ice shelf model, this study investigates tide-topography interactions, energy conversions, and tide-induced cross-slope exchange in the Ross Sea. The model resolves tidal time series and power spectral density that agree well with available mooring data. Through tidal decomposition of modelled tides, we identify a diurnal topographic mode along the Ross Sea slope, characterized by three eddy-like structures. These structures arise because the varying topography of the continental slope induces divergence and convergence in the diurnal surface‑mode tidal flows. This generates sea surface height extremes that persist longer than the time required for geostrophic adjustment, allowing rotating geostrophic flows (i.e., the topographic mode) to develop around them. The topographic mode dominates the water exchange across the slope and yields a net heat transport towards the shelf (~12 TW). The surface and topographic modes can exchange energy with each other, as indicated by alternating positive and negative patches of energy conversion rate with a magnitude reaching 1 W/m². The baroclinic tides in the Ross Sea manifest as bottom-trapped waves over the continental slope and other topographic gradients. The energy of baroclinic tides, primarily converted from the topographic mode, is an order of magnitude smaller than the barotropic tides. The barotropic component accounts for most of the tidal dissipation along the slope (~0.1 W/m²), with a minimal contribution from baroclinic tides. This study identifies tides as an important driver of heat transport onto the Antarctic shelf, which is fundamental for accurately prediction of future Antarctic ice shelf melt and global sea level rise.
This manuscript presents a high-resolution model study of tidal dynamics in the Ross Sea. The results show that steep topography strongly modifies the tidal flow, producing localized eddy-like structures and bottom-trapped waves. These features are associated with enhanced near-bottom energy and vertical shear, highlighting the importance of seabed geometry in redistribution of tidal energy. The study suggests that tides may play an important role in cross-slope exchange and shelfward heat transport.
Model validation is carried out against observational datasets and provides confidence in the model results. Overall, the manuscript is well written and presents interesting results; however, several aspects of the interpretation and presentation could be improved.
Main comments:
- The manuscript would benefit from a dedicated data section describing the observational datasets used for model validation, including the mooring instrumentation, deployment period, and data processing.
- The separation between Results and Discussion is not always clear. The Results section contains interpretive material, while the “Summary and Discussion” section is relatively brief and does not fully explore the physical implications of the results. The manuscript would benefit from either expanding the Discussion or combining the Results and Discussion into a single integrated section. Several important processes are described, but the underlying mechanisms and broader dynamical implications are not always clearly articulated.
Minor comments:
- The Southern Ocean State Estimate version should be specified.
- Please specify which version of the CATS tidal model was used (e.g. CATS2008_v2023).
- Please specify which ERA5 atmospheric variables were used to force the model.
- For figures showing along-isobath structure, please clarify orientation (east/west).
- Please clarify what happens to the eddy-like structures during the transition between flood and ebb tides; do they persist, dissipate, or reverse with the changing flow?
- Please ensure consistent capitalization of axis labels across figures.
- Section 3.3 is rather long and would benefit from subheadings. There are also several repeated statements that could be streamlined.
Line by line comments:
Line 58: Should it be “previous works”?
Line 81: Please specify the SOSE version used.
Line 90: Please confirm the version of the CATS model used.
Line 93: Please specify which ERA5 variables were used for atmospheric forcing.
Line 96: Please clarify why the 2003–2004 period was selected, as it appears to coincide with mooring deployment timing.
Figure 1: Please consider reducing ice shelf transparency to improve readability, particularly for smaller features.
Please clarify the relevance of the 74.5°S reference (critical latitude) in the figure caption.
Line 122: Please justify the use of the deepest observational data point.
Line 129: Please clarify how the time series was filtered.
Figure 3: Please ensure consistent capitalization of axis titles.
Line 173: Please consider moving this material to the Results section.
Line 214: Is this behaviour expected? If so, please add a brief reasoning.
Line 216: Please refer to a figure.
Line 224-225: Please refer to a figure.
Line 233: Should it be Fig. 5c?
Figure 4: As above, consider capitalizing the first letter of axis titles.
Figure 5: Consider removing tidal ellipses, if they are not discussed in the text.
Line 248: Consider referring to a figure: where we can see that is reverses between flood and ebb tides (Fig. 6 a and b, respectively).
Line 267: Please correct the notation for specific heat capacity units (avoid dot product form).
Line 275-279: Consider elaborating on the mechanisms responsible for this behaviour and discuss its potential implications.
Figure 8: Consider consistently capitalizing axis labels.
Line 301: Please clarify that the Ross Sea also lies poleward of the diurnal critical latitude.
Line 304-305: The observed intensification is consistent with the presence of bottom-trapped waves, but it is not uniquely indicative of them. Consider softening this interpretation or discussing alternative explanations.
Line 314:-315 Please provide reasoning for why these thresholds are chosen.
Line 325-326: Please refer to a figure.
Line 328: Consider providing quantitative examples when comparing values.
Figure 9: Please consider capitalizing the first letter of axis titles.
Line 341-351: Please note that this paragraph repeats Lines 321–335 and should be revised/removed.
Line 353: Could the authors provide an example of how much lower the conversion rate is compared with other ocean regions?
Line 369: Please explain why confinement of energy to the bottom boundary is expected to enhance mixing, and discuss the underlying physical mechanism.
Line 402-403: Please elaborate on the implications of the reported "significant numerical uncertainty" for the interpretation of the results.