Sea Ice Drift and Deformation

 


Petra Heil, Jennifer Hutchings, Roger Stevens and Rob Massom


In general the Antarctic pack ice is highly mobile, its drift rate peaking at tens of kilometres per day. For this, and with view to changing environmental conditions, it is important to understand how sea ice responds to wind, waves, tides and other forcing.

Our investigation of sea ice drift and deformation contributes directly to the main scientific objective of SIPEX-2, namely to “expand the multi-disciplinary observational record of, and measurement capability for, East Antarctic sea ice characteristics and processes and thus assess impacts of climate change on the physical and biological elements of the sea ice zone.”

In detail, by deploying one or more fields of drifting buoys in the inner, southern pack ice, this project will study sea-ice kinematics, including the effects of internal ice stress, to investigate the scale-dependency of dynamic processes and to provide observational data to test sea-ice parameterisations in numerical (climate) models.

The buoys will be configured with a variety of sensors. All buoys will provide high accuracy GPS locations, most buoys will measure air temperature, some ice temperature or vertical ice-temperature profiles, some air pressure and some will measure the internal stress within the sea ice.

Buoys within the pack-ice arrays will be staggered to resolve local-to-meso-scale ice motion and deformation. Position, strain and environmental data will be analysed according to Heil et al. (2011) and Hutchings et al. (2010).

The in situ observations will be supplemented by remotely-sensed data, which will provide the regional characterisation of the ice-velocity and ice-deformation distribution. We anticipate sufficient satellite data to derive the meso-scale snapshot of ice velocity using IPADS (IMCORR [IMageCORRelation] Processing, Analysis and Display System) (Giles at al, 2011).

In collaboration with Adam Steer and Jan Lieser, we plan to derive the dynamic contribution to the sea-ice mass balance by combining our buoy-derived information with floe-size distributions derived from the air-borne digital imagery as well as ice-thickness estimates, both to be obtained in the area of our arrays.

The deployments of wave-ice drifters in the nearby marginal ice zone (observing-waves-in-sea-ice) will provide an opportunity to explore the connectedness of the East Antarctic marginal ice zone with the inner pack.

References:
Giles AB, Massom RA, Heil P, Hyland G (2011) Semi-automated feature-tracking of East Antarctic fast ice and pack ice from Envisat ASAR imagery. Remote Sens Environ 115: 2267-2276.

Heil P, Massom RA, Allison I, Worby AP (2011) Physical attributes of sea-ice kinematics during spring 2007 off East Antarctica. Deep-Sea Res II 58: 1158-1171.

Hutchings JK, Geiger CA, Roberts A, Richter-Menge J, Elder B (2010) On the spatial and temporal characterization of motion induced sea ice internal stress. In Proceedings from ICETECH10, International Conference and Exhibition on Performance of Ships and Structures in Ice (www.icetech10.org) by SNAME, 20-23 Sep, Anchorage, AK, 8 pp.