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 Bathymetry MICOM with ice shelves
Weddell Sea
Filchner Depression
Berkner Shelf
Ronne Depression km
MICOM with ice shelves
0.35o grid (9 km x oS)
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
thickness
Berkner Shelf
Layer 15
Filchner Depression
Layer 12
Filchner Ice Shelf

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
Fox sites
Weddell Sea
Sill
ISW
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

10. Filchner Ice Front temperature & velocity at 200 m

11. Filchner Ice Front temperature & velocity at 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 10 velocity FR1 FR2 FR1 FR2 Meridional velocity
Layer thickness (m)
FR1
FR2
Layer 10 velocity
Meridional velocity
& layer number at 75oS
cm/s
FR1
FR2

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