Project 4434

The project has the potential to transform understanding of the physical processes governing drift of the Antarctic ice edge. It proposes to collect the most comprehensive field measurements of waves, winds and currents impacting the ice edge, using state-of-the-art technologies, on a unique three-month marine circumnavigation of the Antarctic. In tandem, it proposes to develop novel methods to analyse interactions between the ice–ocean–atmosphere system around the ice edge from satellite data, and integrate new and improved physics into numerical models, providing accurate predictions of ice-edge drift. The proposed outcomes aim to make significant contributions to filling a key knowledge gap in the field of Antarctic sea ice research, empowering climate studies and operational-safety forecasting.

The team participated in two Antarctic voyages, one during Austral summer and one during winter. They made the most comprehensive measurements to date of winds, waves and currents close to the ice edge, and measured drift of pancake ice floes in a vicinity of the ice edge during a storm event. Using the data captured they have gained insights into the occurrence of extreme waves in the Southern Ocean, and on the distribution of pancake floe sizes. They are compiling datasets on environmental conditions during the voyages, and developing models to gain understanding of the ice drift close to the ice edge.

The team is analysing the comprehensive set of winds, waves and currents measured at the edge of the marginal ice zone during two Antarctic voyages in 2017: one in summer (February, as part of the Antarctic Circumnavigation Expedition) and one in winter (July, on the SA Agulhas II). During the winter voyage, we encountered and measured the effect of a series of extreme polar cyclones on the marginal ice zone. Intense wave-in-ice activity was detected in 100% ice concentration and over 100km in from the edge, indicating the limitations of a concentration-based definition of the marginal ice zone. We measured the largest sea ice drift velocity in the Southern Ocean. The data have been used to develop understanding and models of pancake ice drift.

We participated in and led three Antarctic voyages, and compiled the most comprehensive databases of winds, waves, currents and ice properties close to the Antarctic ice edge and in the highly dynamic marginal ice zone, recording the fastest ice drift speed and largest wave-in-ice heights in the Southern Ocean to date. We captured data during a series of explosive polar cyclones, and gained understanding of the rapid and widespread changes ice-landing cyclones have on the marginal ice zone. We pioneered the use of onboard stereo-camera systems to monitor the ice cover and waves-in-ice, and used our measurements to generate the first assessments of the floe size distribution and extreme wave probabilities in the marginal ice zone during the Antarctic winter ice expansion. We showed pancake ice drift correlates with winds, with a strong inertial signature superimposed, and the importance of waves in maintaining an unconsolidated ice cover. We developed a numerical drift model to back the measurements and showed it is capable of predicting ice drift accurately for periods up to two days.