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Ocean circulation and water mass transformation beneath Filchner-Ronne Ice Shelf:

Ocean circulation and water mass transformation beneath Filchner-Ronne Ice Shelf: Results from a 3-D ocean model. Keith Makinson. British Antarctic Survey, Cambridge, U.K. FRIS sub-ice shelf circulation (OBS). Bathymetry contours in 100’s of metres ( after Nicholls and Østerhus, 2004 ).

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Ocean circulation and water mass transformation beneath Filchner-Ronne Ice Shelf:

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  1. Ocean circulation and water mass transformation beneath Filchner-Ronne Ice Shelf: Results from a 3-D ocean model Keith Makinson British Antarctic Survey, Cambridge, U.K.

  2. FRIS sub-ice shelf circulation (OBS) Bathymetry contours in 100’s of metres (after Nicholls and Østerhus, 2004)

  3. Model domain km Bathymetry Weddell Sea Berkner Shelf Ronne Depression Filchner Depression • MICOM with ice shelves • 0.35o grid (9 km x 9 km @ 76.5oS) • 15 isopycnic layers + mixed layer • Season surface salinity forcing • Tidal forcing • Run for 20 years

  4. HSSW inflow & pooling in deep depressions Layer 16 Weddell Sea Layer 15 Layer thickness Berkner Shelf Filchner Depression Filchner Ice Shelf Layer 12

  5. How do dense water masses escape the deep depressions ? (1) Interact with ice shelf (i.e. follow Gade line) (2)Mix with other water masses Weddell Sea Sill ISW Fox sites Ronne Depression Ronne Ice Shelf Filchner Ice Shelf

  6. Filchner Depression – mean annual circulation Meltwater fraction (ppt)

  7. Filchner Depression – mean annual circulation Meltwater fraction (ppt)

  8. Filchner-Ronne Ice Front CTD sections From Gammelsrod et al, 1994

  9. Filchner Ice Front temperature & velocity at 600 m oC 600 m

  10. Filchner Ice Front temperature & velocity at 200 m oC 200 m

  11. Filchner Ice Front temperature & velocity at 800 m oC 800 m

  12. Filchner Ice Front mixing (1) Interact with ice shelf i.e. follow Gade line (2) Mix with other water masses Coastal Current Berkner Shelf Sill ISW Fox sites Filchner Ice Front

  13. Meridional velocity & layer number at 77.5oS cm/s 600m

  14. Filchner Sill Layer thickness (m) FR1 FR2 Layer 10 velocity cm/s FR1 FR2 Meridional velocity & layer number at 75oS

  15. FRIS sub-ice shelf circulation (Obs)

  16. FRIS sub-ice shelf circulation (Model)

  17. Summary • Dense water inflows routes similar to observations • Recirculation in Filchner Depression limited to ice front region • Primary ISW outflow occurs on eastern side of the depression • Convergence and mixing of water masses at Filchner Ice Front results in ISW that can escape over the sill • The northward flow of ISW is gathered along to the eastern slope of Filchner Depression

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