An ice shelf is a floating marine equivalent of an ice sheet, and because it floats it leaves virtually no traces, except if it runs aground. Today there are some really large ice shelves left in the Antarctic, but there are not much left of those in the Arctic Ocean.

During the SWERUS-C3 expedition in 2014 researcher at Stockholm University, in collaboration with researchers in Gothenburg, the US and Russia could, using the icebreaker Oden's advanced sonar, see traces from the large ice shelves of the Ice Age on the seabed in the central Arctic. The results show that the size of the ice shelves of the Arctic Ocean often surpassed those found around the Antarctic today, which confirms the theoretical hypothesis presented in the 1970s. The ice was about one kilometre thick, and when it passed over the Lomonosov Ridge, a mountain chain on the seabed, it left deep and up to several hundred metres wide traces, as if an enormous rake had dragged over the sea floor.

The article “Evidence for an ice shelf covering the central Arctic Ocean during the penultimate glaciation”, is published in the journal Nature Communications.

The results have also been presented in Nature’s News & views, “Climate science: A great Arctic ice shelf”.