Photo:  Seaglider by Emma Bone

In an unprecedented study starting in December 2018 and running until February 2020, a fleet of robotic ocean gliders will attempt to occupy and collect vital measurements from the least studied place on the planet - the frigid ice covered Antarctic waters. The gliders will set out to measure how the icy Antarctic ocean absorbs heat, and other climate essential properties, from the atmosphere.

During winter, Antarctic sea ice expands as an extension of the continent over an area of the sea large enough to cover 14 South Africa's. Almost all this sea ice melts away during the summer, leaving a layer of freshwater on the ocean surface thousands of kilometres wide, but only a few tens of meters thick. The freshwater is very light compared to seawater, and so acts as a blocking mechanism for vertical mixing, thereby changing the ocean's ability to take up heat from the atmosphere. This study will provide key observations to help us understand just how the sea ice melt grows laterally and deteriorates, thereby altering ocean heat uptake and impacting the climate.

Photo:  Seaglider by Louise Biddle

Beyond this, things can get pretty complicated, sea ice melt and growth occurs in response to ocean temperatures, and so as we move towards a warming climate, the ocean will absorb more heat, directly changing sea ice growth and melt behaviour. These measurements will inform researchers from the UCT's Department of Oceanography, as well as their international partners just how the ocean will react to and influence a changing climate.

Observationally, the waters off Antarctica are the most difficult to measure. The vast remoteness of the Antarctic and rapid ice growth and drift means that the required long-term observations are not obtainable from ships, which only go down there for a few weeks a year. So instead we will send down autonomous underwater vehicles, called gliders. The primary glider used for this study is called a Seaglider, designed to be small - about 1.5 m long - and operate on battery power, meaning they can sample the ocean for many months without human intervention. Their bullet-shaped design helps them fly through the ocean, profiling the water column by changing their buoyancy to become heavier or lighter than seawater. They hit the surface every six hours and “call” the researchers via satellite communications, allowing access to the dive information and scientific data in real-time.

The gliders are entirely self-sufficient and give us a profile of the ocean every few hours. This study will provide unprecedented data for us as we can now see the impacts of the hurricane force winds which sweep through a wind belt called the "Screaming Sixties." These are the strongest winds in the world and act in a similar way to a blender at the ocean surface by mixing the fresh surface waters with saltier waters below. Another research gap we are trying to close is to find out just how these storms drive a mixing of heat from the surface down the water column.

The project ROAM-MIZ (Robotic Observations and Modelling of the Marginal Ice Zone) is co-lead by Associate Professor Sebastiaan Swart (now at the University of Gothenburg) and Dr. Sarah Nicholson (now at the Southern Ocean Carbon and Climate Observatory in Cape Town supported by the South African National Antarctic Program), who both obtained their PhD's from UCT. Further collaborators from the United States, the UK and Norway make this project a truly global effort. UCT PhD candidate Isabelle Giddy and Post Doctoral Researcher Marcel du Plessis are both heavily involved in the project and will have their eye's fixed on their computers each time a glider calls home to provide new data from half way across the world. The latest data and glider locations are made available for anyone who is interested. Just head over to www.roammiz.com to view the latest data and glider whereabouts. You can also follow the updates from Twitter at @PolarGliders and @SOCCOgliders.

Story by: Marcel du Plessis