The Arctic Ocean is surrounded largely by continents, and the Fram Strait (sill depth 2,500 m) is the only deep connection to the Nordic Seas and further south to the North Atlantic across the Greenland–Scotland Ridge (sill depth approximately 950 m). This configuration strongly limits water exchange with the other world oceans, in particular in glacials when other shallower straits are closed. Based on 230Th and 10Be concentration profiles of sediment cores from the Arctic Ocean and Nordic Seas deep basins, Geibert et al.1 claim that during two previous glacial episodes, the connections were blocked by an approximately 1-km-thick ice shelf with only freshwater underneath. Here we put forward several strong arguments that contradict this interpretation and render it unlikely that the Arctic Ocean and Nordic Seas were filled by freshwater during the intervals discussed. |
