Sea ice-free corridors for large swell to reach Antarctic ice shelves

Abstract

Sea ice can attenuate Southern Ocean swell before it reaches Antarctic ice shelves and imposes flexural stresses, which promote calving of outer ice-shelf margins and influence ice shelf stability. An algorithm is developed to identify sea ice-free corridors that connect the open Southern Ocean to Antarctic ice shelves from daily satellite sea ice concentration data between 1979–2019. Large swell in the corridors available to impact the ice shelves is extracted from spectral wave model hindcast data. For a selection of ice shelves around the Antarctic coastline, corridors are assessed in terms of duration and areal extent. The availability of large swell to impact certain ice shelves through the corridors is evaluated from spectral wave data for daily statistical properties and the number of large swell days per year. Results integrated over a large number of ice shelves are used to assess overall trends. Large variations are found between individual ice shelves for both corridors and available swell, with contrasting trends between the West and East Antarctic Ice Sheets. The findings indicate ice shelves likely to experience prolonged periods of appreciable outer margin flexure due to large swell action, such as the Fimbul, Shackleton and Ross Ice Shelves, which could exacerbate climate-driven weakening and decreasing buttressing capacity, with implications for sea-level rise.

Modeling Ocean Wave Transfer to Ross Ice Shelf Flexure

“…Teder et al. (2022) found swell with significant wave heights H s > 6 m, where $$${H}_{\mathrm{s}}={H}_{\mathrm{s}}\left({S}_{\text{sw}}\right)=4\sqrt{{m}_{0}\left({S}_{\text{sw}}\right)}\quad \text{such}\,\text{that}\quad {m}_{0}(S)=\int \nolimits_{0}^{\infty }S(\omega )\mathrm{d}\omega ,$$$ can reach the RIS through sea ice free corridors for over 5 days a year (on average over the satellite era), which is ≈10% of the days sea ice free corridors exist for the RIS. Therefore, the peak frequency f p ≡ ω p /(2π) = (1/13) Hz is chosen to give H s ≈ 6.76 m.…”

“…Free surface conditions hold at the water surface, such that $$${\partial }_{z}{\Phi}={\partial }_{t}\xi \quad \text{and}\quad {\partial }_{t}{\Phi}=-g\xi \quad \text{for}\quad -l< x< 0,$$$ where ξ ( x , t ) for − l < x < 0 represents the free surface displacement. The second component of Equation assumes sea ice does not occupy the free surface, that is, a sea ice free corridor leads to the shelf front (Teder et al., 2022), although attenuation due to sea ice could be incorporated using the model of, for example, Bennetts and Squire (2012a, 2012b).…”

“…where ξ(x, t) for −l < x < 0 represents the free surface displacement. The second component of Equation 3assumes sea ice does not occupy the free surface, that is, a sea ice free corridor leads to the shelf front (Teder et al, 2022), although attenuation due to sea ice could be incorporated using the model of, for example, Bennetts andSquire (2012a, 2012b).…”

“…0053 is the modified Phillips constant, γ = 3.3 is the peakedness, and υ = 0.07 (for ω < ω p ) and =0.09 (for ω > ω p ) is the spectral width Teder et al (2022). found swell with significant wave heights H s > 6 m, where…”

Antarctic Landfast Sea Ice: A Review of Its Physics, Biogeochemistry and Ecology

“…Waves are another missing component from most regional ice‐ocean coupled models, and likely control the nature and timing of fast‐ice breakout in many regions (Crocker & Wadhams, 1989a). A further benefit in simulating wave‐ice interaction is that the resulting wave field incident upon ice shelves may also be used for studies of ice shelf‐wave interaction (including wave‐induced flexure, calving and disintegration; Teder et al., 2022).…”