Ice Sheets and Sea Ice….what's the difference?

The Brunt Ice Shelf floats on the sea but it's not sea ice. So what's the difference? The Brunt Ice Shelf is a whopping 110 meters thick as measured below the Halley V site. The ice spills off the continent like a huge flat glacier and makes it's way across the ocean until it reaches a point where temperature can no longer sustain it and huge chunks break off as icebergs and float away. Halley V actually moves 1.5 meters or so every day in a westerly direction as the ice it rests on travels seaward. One day the ice Halley V rests on will break off as an iceberg and the base will float off. As explained last week, the Lifetime of Halley project as run by Ryan Anderson studies the movement of the Brunt Ice Shelf by utilising many remote GPS sites that log their current position down to the centimetre. Collating the results from the GPS sites can provide an insight into the general movement of the Brunt.

Halley V sits on the Brunt Ice Shelf. There be sea 110 meters below!

Sea ice is seasonal ice that forms at the edge of the ice shelf and, as its name suggests, forms when the sea freezes. The sea ice is only tens of centimetres thick and gradually breaks up and dissipates during the summer months especially when the wind starts to pick up. The picture below, taken by our wintering chef Chris Walton, shows the edge of the Brunt and the sea ice on which the penguins breed.

The edge of the Brunt at Windy Bay by Chis Walton