Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain
the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in
Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles
and JavaScript.
Over the past 15 million years, Arctic Ocean circulation has exhibited two distinct modes: during the interglacial periods of the past two million years, including the present, Arctic intermediate water was mainly derived from North Atlantic inflow. By contrast, between 15 and 2 million years ago, and during glacial periods thereafter, brine formation on the Eurasian shelves contributed substantially to Arctic intermediate water.