Oral Presentation AMOS Annual Meeting and International Conference on Tropical Meteorology and Oceanography

Storm events and drift of pancake floes at the edge of the marginal ice zone (#113)

Alberto Alberello 1 , Luke Bennetts 1 , Petra Heil 2 , Clare Eayrs 3 , Marcello Vichi 4 , Keith MacHutchon 4 , Miguel Onorato 5 , Toffoli Alessandro 6
  1. University of Adelaide, Adelaide, SA, Australia
  2. Australian Antarctic Division & ACE – CRC, Hobart, TAS, Australia
  3. New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
  4. University of Cape Town, Rondenbosch, South Africa
  5. University of Turin, Turin, Italy
  6. The University of Melbourne, Parkville, VIC, Australia

During winter, sea-ice advances over the Southern Ocean in the form of small floes of circular shape with raised edges, known as pancake floes. Pancake ice may extend hundreds of kilometres in from the ice edge (in a region known as the marginal ice zone), constituting a significant portion of the winter Antarctic sea-ice mass budget, and thus playing a pivotal role in regulating heat and momentum exchange for the Southern Ocean. The pancakes are sustained by intense storm-wave action, which prevents their congelation. Contemporary models struggle to reproduce the winter advance of the ice edge under the action of winds, waves or currents. Moreover, limited observations are available for the drift of the loosely connected and, mostly, unconstrained pancake floes. In July 2017, the South African icebreaker Agulhas II conducted an exploration of the winter marginal ice zone, south of Good Hope, during which a pair of wave buoys were deployed on pancake floes ~100km in from the ice edge. The buoys recorded the ice drift over ten days, capturing three separate storm events. Data highlighted: (i) unprecedented high drift velocities; (ii) a high correlation of ice drift with the surface wind; and (iii) the presence of a strong inertial signature in the motion of the pancakes. Drift data are interpreted in the framework of the free drift approximation to provide an estimate of wind and ocean drag for pancake floes under storm conditions.