From AMS Glossary
A form of tabular iceberg found in the Arctic Ocean, with a thickness of 30–50 m and from a few thousand square meters to 500 km2 in area.
Ice islands often have an undulated surface, which gives them a ribbed appearance from the air.
Armstrong, T., B. Roberts, and C. Swithinbank 1973. Illustrated Glossary of Snow and Ice. Scott Polar Research Institute, Special Pub. No. 4, 2d ed., The Scholar Press Ltd., Menston Yorkshire, UK.