“Shedding light” on the Atlantic-Southern Ocean sea ice marginal zone

Thursday, December 8th, 2016

8 December 2016:  Contributed by A/Prof Marcello Vichi

SCAR funding for capacity building in South Africa

1 SA pancake collection 2016On the night of 21 July 2016, South Africa initiated its own contribution to the study of the marginal ice zone (MIZ) in the Atlantic sector of the Southern Ocean. It was deep dark at about 56oS along the Greenwich meridian when the SA Agulhas II passed abruptly the external MIZ, with sea ice concentration turning swiftly from open water conditions to about 50%.

The University of Cape Town (UCT) team was led by the affiliated civil engineer Keith MacHutchon and comprised ice analyst Trond Robertsen of the Norwegian Ice Service, civil engineering postgrad students Emmanuel Omatuku Ngongo and Devin Dollery, oceanography postgrads Ehlke de Jong, Casey Lyttle and Chloe Blyth, and a seconded technician from France, Emeline Cadier.

SA frazil sampling 2016The expedition schedule allowed little time in the sea ice and the data collection was to be conducted under the spotlights and surrounded by full darkness.  Seven pancake-ice samples were lifted from the freezing cold water using lifting baskets. When the frazil needed collecting, members of the team were suspended over the ice by crane in the middle of the night – not a feat for the faint of heart!

The quest started not many months before, when a multi-disciplinary group of scientists from the Department of Oceanography, the Department of Civil Engineering and the Marine Research Institute at the University of Cape Town, led by A/Prof Marcello Vichi, Dr Keith MacHutchon and Dr Sebastian Skatulla, joined forces to take advantage of the expeditions funded by the South African National Antarctic Programme (SANAP) during wintertime.

Winter expeditions are rare in the Atlantic sector and, since the International Polar Year, a few sea ice observations have been done in this region. Despite the availability of a state-of–the-art icebreaker, the RV SA Agulhas II, which is used for research as well as to serve the Antarctic base, there is almost no expertise in South Africa on sea ice observations and sampling. Capacity building is therefore the first and foremost task to be undertaken. An expert sea ice observer from Norway joined the Cape Town team thanks to funding made available by SCAR and by SANAP.

SA bridge weather 2016Trond Robertsen trained the participants on the ASPeCt (Antarctic Sea Ice Processes) protocols with a series of daily morning meetings on the way to the MIZ, during which information and lectures were given. Due to the lack of bandwidth on board, it was not possible to use the ice charting system to do ice analysis based on received satellite imagery. It clearly emerged that improvements to the communication system are necessary if proper sea ice research is to be done in the future. Observations were set to be at the top bridge, with rotating shifts and photos to be taken to port, ahead and starboard. ASPeCt observational spreadsheets where filled in and checked for consistency by the chief sea ice observer.

This first voyage was very limited in scope, but it has afforded South Africa the opportunity of linking with the ASPeCt community and building an initial expertise in Antarctic sea ice. This will complement the data on air-sea fluxes currently collected by the Southern Ocean Carbon & Climate Observatory during the cruises. Thanks to another collaboration with SYKE (the Finnish Environment Institute) and the RV Aranda, the UCT PhD student Tshikana Rasheshlomi was hosted on board of RV Aranda for a training on sea ice observations during the February cruise, the very first time on sea ice for an African student.

SA MIZ expeditionsThe next voyage to the Antarctic base left Cape Town harbour on 30 November 2016. There was not much time to organize a proper sea ice sampling for this expedition, but there is a growing interest in the community to have a dedicated project on sea ice as part of SANAP for 2018. In the meanwhile, a further collaboration with the engineering team from Stellenbosch University and from Aalto University, Finland, led by Dr Annie Bekker and Dr Mikko Suominen, will allow collecting a new detailed set of sea ice observations in the eastern Weddel Sea for the entire duration of the cruise (the return is expected on 7 February 2017). As part of their study on ship vibrations, they will gather images of sea ice floes that will complement the recordings and observations planned by the UCT team.

Currently, the training sponsored by SCAR has been contributing to two BSc Honours theses, two MSc and one PhD theses at the University of Cape Town and more are expected over the next years.

For more information and additional images, see the news item on the University of Cape Town website.

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