The Hillary Canyon and the Iselin Bank (Eastern Ross Sea, Antarctica): Alongslope and Downslope Route For Ross Sea Bottom Water

Monday, 14 December 2015
Poster Hall (Moscone South)
Laura De Santis1,2, Andrea Bergamasco3, Ester Colizza4, Riccardo Geletti2, Flavio Accaino2, Nigel Wardell2, Elisabetta Olivo2, Lorenzo Petronio2, Stuart A Henrys5, Jenny Black5, Robert M Mckay6 and Gualtiero Bohm2, (1)Ist Nazionale Oceanografia, Sgonico, Italy, (2)National Institute of Oceanography and Applied Geophysics OGS, Geophysics, Trieste, Italy, (3)CNR-ISMAR Inst. of Marine Sciences, Bologna, Italy, (4)University of Trieste, Mathematics and Geosciences, Trieste, Italy, (5)GNS Science, Lower Hutt, New Zealand, (6)Victoria University of Wellington, Wellington, New Zealand
The modern seabed of the Antarctic continental slope generally does not show a rugged geomorphology. Channel systems incise the lower continental rise, but in most cases they are inherited features formed as channel-levee turbiditic systems during past, more temperate times.

The Hillary Canyon cuts the eastern Ross Sea continental slope and rise, to the Southeast of the Iselin Bank, and is directly connected to the Glomar Challenger Trough on the continental shelf. Cold dense salty water forms today in the Ross Sea polynya, spreads below the Ross Ice Shelf, becomes supercooled, fills up the landward deepening Glomar Challenger Trough and then spills over the sill of the shelf edge and flows downslope, often along the Hillary Canyon, in a geostrophic way, deviated westwards by the Coriolis Force, but sometimes also with a cascading a-geostrophic behaviour. This supercold water signal was found on the continental slope down to 1200 m depth. The shape of this tongue of modified ISW, whose thickness reaches up to 100 m, is very narrow, suggesting that the overflow occurs in very localized areas along the slope.

Here we combine seismic stratigraphy analysis of multichannel seismic reflection profiles, box and gravity cores in the Hillary Canyon and along the eastern flank of the Iselin Bank, with seabed bathymetry and numerical modelling of thevertical and spatial distribution of the water masses, in order to identify modern and past pathways of the Ross Sea Bottom Water current.

The results of this work show that the Hillary Canyon and the sediment mounds that formed along its flanks have been active since early Miocene times. Sediment drift-moat features and sediment waves are indicative of strong Northwest bottom currents reworking the seabed sediments at different water depths along the slope, possibly since the late Miocene. These sediment drifts are some of the targets of the IODP proposal 751-full.