The British Antarctic Survey (BAS) has redelivered a polar research vessel earlier than scheduled to its owner, GC Rieber Shipping, which plans to sell it.

The 80-metre Ernest Shackleton (built 1995) has been on charter to BAS since its delivery and has been used mainly as a logistics ship for resupplying BAS’ stations.

If the sale goes through, GC Rieber said it expects a positive cash effect of about NOK 140m ($16.4m) in the second quarter this year.

The sale to an unnamed "international buyer" is conditional on receiving certain regulatory approvals, the owner said.

In October 2017, BAS declared its fifth and final option to extend the vessel's bareboat charter for 12 months until August this year.