  Glacial cycles redistribute water between oceans and continents causing
pressure changes in the upper mantle, with consequences for melting of Earth's
interior. Using Plio-Pleistocene sea-level variations as a forcing function,
theoretical models of mid-ocean ridge dynamics that include melt transport
predict temporal variations in crustal thickness of hundreds of meters. New
bathymetry from the Australian-Antarctic ridge shows significant spectral
energy near the Milankovitch periods of 23, 41, and 100 ky, consistent with
model predictions. These results suggest that abyssal hills, one of the most
common bathymetric features on Earth, record the magmatic response to changes
in sea level. The models and data support a link between glacial cycles at the
surface and mantle melting at depth, recorded in the bathymetric fabric of the
sea floor.
