Modelling activities

1.  Petermann ice shelf – melting from below

Petermann Glacier flows from the land into the ocean within Petermann Fjord, where it forms a floating ice shelf. The ice shelf is constantly fed with new ice from the glacier, and loses ice due to calving icebergs at the end of the ice shelf, melting at the surface (due to relatively warm air) and melting at the bottom (due to relatively warm water). Around 80% of ice lost from Petermann Glacier is caused by melting at the bottom of its ice shelf by warm ocean water.

We know that there are several prominent along-shelf channels in the base of the ice shelf, and we think that these play an important role in the bottom melting process. We are conducting a series of experiments with a computer model of the water-filled cavity under Petermann’s floating ice shelf to test this hypothesis.  The first results show that the introduction of channels to the base of an ice shelf changes the parts of the shelf that melt and also reduces the total amount of melting that occurs. This suggests that the presence of channels at the base of an ice shelf may stabilize it and prevent it from being melted away.

Melt rate (colours) and flow (arrows) underneath an ice shelf with no channels (left) and with four channels (right). When there are no channels, the water flows across to the right hand side of the fjord and then along underneath the ice shelf against the right hand fjord wall. The highest levels of melting occur under the flow on the right hand side. When channels are introduced, the water flows up the channels instead, leaning on the right hand side of each channel, where the melting is also greatest.

This work is being carried out by Tom Millgate together with our collaborators Paul Holland and Adrian Jenkins at the British Antarctic Survey (BAS).

2.  What determines the circulation and the flux of fresh water through Nares Strait and the rest of the Canadian Archipelago?

We are also conducting experiments with a computer model of the ocean circulation and sea-ice in the region to establish what controls the flow of freshened sea water and ice from the Arctic to the North Atlantic.