Ocean circulation and mantle melting controlled by radial flow of hot pulses in the Iceland plume

Convection of the mantle influences elevation at the Earth's surface. For example, in the North Atlantic Ocean, V-shaped ridges of thickened oceanic crust that straddle the mid-ocean ridge are thought to arise from variations in the underlying mantle properties(1). However, the detailed relationship between these V-shaped ridges and convective circulation is uncertain. Here we use measurements of residual water depth-a proxy for crustal thickness-and basaltic geochemistry to assess factors responsible for ridge formation. We find a correlation between basalt composition and crustal thickness that is best explained if V-shaped ridges are formed by the passage of unusually hot pulses of mantle away from Iceland. We also show that ocean circulation patterns over the past 7 million years, recorded by flow of the Northern Component Water(2-4) from the Norwegian Sea into the Atlantic Ocean and the accumulation of thick drifts of sediment(5), are controlled by variations in the elevation of sea floor between Greenland and Iceland. We suggest that pulses of hot mantle also drove periodic uplift of the sea floor, and moderated the export of water and sediment into the North Atlantic Ocean. Diverse observations can therefore be explained if blobs of mantle, 25 degrees C hotter than the background plume temperature, travelled up the conduit beneath Iceland and spread out radially at velocities of 40 cm yr(-1).